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235 Commits

Author SHA1 Message Date
06678a5888 #1617 update license headers 2021-01-24 20:07:40 +02:00
11d0912c6e #1617 merge dto pattern examples 2021-01-24 19:57:21 +02:00
3adc3cda05 update gitignore (#1632)
.checkstyle files are being tracked which should not be
2021-01-24 11:17:05 +02:00
18a1a725ee #1469 Add lambda expressions implementation for Strategy Pattern (#1631)
* #1469 Add Strategy Pattern lambda implementation

After Java 8.
Also take advantage of enum

* #1469 Update class diagrams

* #1469 Update README.md

Add lambda programmatic example

* #1469 Remove unused imports

Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>
2021-01-19 12:06:26 +05:30
25ed2540f4 docs: add demirhalil as a contributor (#1630)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
2021-01-16 21:00:23 +02:00
aa46e119d6 Fix flag image size 2021-01-16 20:55:20 +02:00
7e56491e92 #1625 Turkish translation - initialization part (#1629)
* #1625 init Turkish translation and add the flag

* #1625 update the Main README.md for Turkish translation

* #1625 add Turkish translation for README.md

Co-authored-by: Halil Demir <halil.demir@zalando.de>
2021-01-16 20:49:35 +02:00
6918a4bac2 docs: add ignite1771 as a contributor (#1626)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>
2021-01-13 13:31:11 +05:30
dea7ecfb7a #1317 Special Case Pattern (#1624)
* #1317 Add Special Case Pattern

To focus on pattern itself, I implement DB and
maintenance lock by the singleton instance.

* #1317 Add special cases unit tests

Assert the logger output
(ref: https://stackoverflow.com/a/52229629)

* #1317 Add README.md

Add Special Case Pattern README

* #1317 Format: add a new line to end of file

Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>
2021-01-13 13:06:21 +05:30
bbc4fdfc24 docs: add tkhadir as a contributor (#1623)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>
2021-01-04 19:42:58 +05:30
829cd41455 #1620 french translation - initialization part (#1622)
* 🚀 init fr translation

* #1620 evo add french translation - main part

* #1620 evo add french translation - main part

* #1620 evo french translation - add french flag

* Update README.md

* Update README.md

* #1620 add cn and kr flags

* Update README.md

* Update README.md

* Update README.md

* Update README.md
2021-01-04 19:27:32 +05:30
85a05dd718 docs: add warp125 as a contributor (#1619)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
2020-12-20 20:20:51 +02:00
0c66e48d81 README.md translated into Korean (#1582)
* Translate README.md via GitLocalize

* Translate README.md via GitLocalize

* Update README.md

* Translate README.md via GitLocalize

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Translate README.md via GitLocalize

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Translate README.md via GitLocalize

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Translate README.md via GitLocalize

* Update README.md

Co-authored-by: mt-gitlocalize <mt@gitlocalize.com>
2020-12-20 20:18:23 +02:00
801006337a docs: add ruchpeanuts as a contributor (#1618)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
2020-12-13 17:35:37 +02:00
2aa4c963eb Update README.md (#1598)
Factory method is updated with real world examples
2020-12-13 17:33:43 +02:00
8632962362 docs: add siavashsoleymani as a contributor (#1616)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>
2020-12-09 13:11:15 +05:30
5bc61c8c28 #1569 DTO pattern implementation using Enums (#1570)
* #1569 DTO pattern implemented using Enums

* #1569 DTO pattern implemented using Enums

* #1569 adding some java docs

* #1569 some changes in java doc and code style

* #1569 some changes in java doc and code style

* #1569 some changes in java doc and code style

* #1569 some changes in java doc and code style

* #1569 adding suggested extra line

* #1569 license added to pom.xml

* #1569 more checkstyle problems resolved

* #1569 more checkstyle problems resolved

* #1569 more checkstyle problems resolved

Co-authored-by: siavashsoleymani <siavash.soleimani@snapp.cab>
Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>
2020-12-09 12:51:24 +05:30
a94615ac54 docs: add viveksb007 as a contributor (#1613)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
2020-12-08 10:58:39 +05:30
14c4710435 Implemented Registry pattern (#1543)
* #1310 Implemented registry pattern

* fixed parent pom version

* added empty line in registry.urm.puml

Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>
2020-12-08 10:34:42 +05:30
428cbc1027 docs: add jeff303 as a contributor (#1612)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
2020-12-07 20:25:59 +02:00
a118a995ec docs: add omk13 as a contributor (#1611)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
2020-12-07 19:58:05 +02:00
759c99d078 JUnit4 to JUnit5 (#1589)
* Getting @Test from JUnit5 instead of JUnit4

* Changed FixedStepGameLoopTest.java imports and tests to JUnit5

* JUnit4 to JUnit5

* JUnit4 to JUnit5

* JUnit4 to JUnit5

* JUnit4 to JUnit5
2020-12-07 19:55:13 +02:00
e9f73bcf0b Translation zh (#1610)
* add state and callback pattern

* add command and template-method pattern

* add iterator pattern

* add bridege and DI pattern

* fix issue #1600

Co-authored-by: Mike <admin@xiaod.info>
Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
2020-12-06 16:13:48 +02:00
29ceac2fb0 Update README.md (#1592) 2020-12-05 10:56:00 +02:00
7255c2c5e7 docs: add Anurag870 as a contributor (#1609)
* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

* Update README.md

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>
Co-authored-by: Ilkka Seppälä <ilkka.seppala@gofore.com>
Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
2020-12-05 10:50:09 +02:00
68308dc550 Update README.md (#1590) 2020-12-05 10:34:49 +02:00
1e10951c23 Translation zh (#1597)
* add state and callback pattern

* add command and template-method pattern

* add iterator pattern

Co-authored-by: Mike <admin@xiaod.info>
2020-12-04 20:03:14 +02:00
f3c876ed2e Merge pull request #1607 from iluwatar/all-contributors/add-gkulkarni2020
docs: add gkulkarni2020 as a contributor
2020-12-04 15:48:40 +02:00
ecd1a5d07f docs: update .all-contributorsrc [skip ci] 2020-12-04 13:47:58 +00:00
8b15c24753 docs: update README.md [skip ci] 2020-12-04 13:47:57 +00:00
f5a6161044 Merge pull request #1604 from gkulkarni2020/master
Word mistake in factory/README.md #1601
closes #1601
2020-12-04 14:17:32 +05:30
76eefa80b5 Merge branch 'master' into master 2020-12-04 13:30:11 +05:30
c282ab80fd Merge pull request #1606 from iluwatar/all-contributors/add-ibrahimAlii
docs: add ibrahimAlii as a contributor
2020-12-01 22:48:24 +02:00
1edfb44642 docs: update .all-contributorsrc [skip ci] 2020-12-01 20:47:33 +00:00
e185c497ac docs: update README.md [skip ci] 2020-12-01 20:47:32 +00:00
d5a054c1f8 Merge pull request #1605 from iluwatar/all-contributors/add-OrangePants-R
docs: add OrangePants-R as a contributor
2020-11-30 16:57:52 +02:00
ced7a9deb0 docs: update .all-contributorsrc [skip ci] 2020-11-30 14:57:00 +00:00
90c6cf94d5 docs: update README.md [skip ci] 2020-11-30 14:56:59 +00:00
996bd937fb Merge pull request #1576 from OrangePants-R/master
issue 525: attach tutorialspoint link to iterator pattern
2020-11-30 16:55:19 +02:00
7931471b99 Word mistake in factory/README.md #1601 2020-11-30 15:26:01 +05:30
b8ecbaa451 Merge pull request #1603 from iluwatar/all-contributors/add-grzesiekkedzior
docs: add grzesiekkedzior as a contributor
2020-11-28 15:09:18 +02:00
fb4df48cb3 Merge branch 'master' into all-contributors/add-grzesiekkedzior 2020-11-28 15:08:15 +02:00
96fadf3bd7 docs: update .all-contributorsrc [skip ci] 2020-11-28 13:04:26 +00:00
dd599595cc docs: update README.md [skip ci] 2020-11-28 13:04:25 +00:00
fcd7785f0d Merge pull request #1568 from ohbus/master
Update Pull Requests CI trigger behaviour
2020-11-28 14:38:00 +02:00
2432d120b4 Merge pull request #1602 from iluwatar/all-contributors/add-eimanip
docs: add eimanip as a contributor
2020-11-28 14:25:41 +02:00
4b18e223cd docs: update .all-contributorsrc [skip ci] 2020-11-28 12:24:58 +00:00
13c6de036f docs: update README.md [skip ci] 2020-11-28 12:24:57 +00:00
6f979d0cb2 Fix version number class diagram not showing 2020-11-24 08:10:34 +02:00
f084f8bf41 Merge pull request #1599 from iluwatar/all-contributors/add-manannikov
docs: add manannikov as a contributor
2020-11-23 22:38:24 +02:00
6c95868b8d docs: update .all-contributorsrc [skip ci] 2020-11-23 20:37:49 +00:00
4c7f1b7822 docs: update README.md [skip ci] 2020-11-23 20:37:48 +00:00
0c44b53909 Merge pull request #1563 from manannikov/Issue#1284
#1284 Implement Version Number pattern
2020-11-23 22:35:43 +02:00
9ead3adf73 #1284 Divide tests 2020-11-23 20:59:00 +02:00
97e3a3debc #1284 Use local variable inference 2020-11-23 19:42:50 +02:00
43ed09015d Add missing license header 2020-11-22 21:14:53 +02:00
7eee546208 Update README.md 2020-11-08 19:39:21 +02:00
dc31960710 Remove unused logger objects 2020-11-08 19:37:15 +02:00
7c0fdad5a2 Merge pull request #1531 from ravening/command-functional
Refactor the command pattern to use lambda functions
2020-11-08 19:33:48 +02:00
5a8933ea17 Merge pull request #1534 from swarajsaaj/#1510-Circuit-Breaker-Refactoring
#1510 Improvements done in Circuit Breaker
2020-11-07 20:04:47 +02:00
d02233f0b7 Merge pull request #1594 from iluwatar/all-contributors/add-akashchandwani
docs: add akashchandwani as a contributor
2020-11-07 14:36:54 +02:00
d42bcab9fc docs: update .all-contributorsrc [skip ci] 2020-11-07 12:34:36 +00:00
77b2ff2150 docs: update README.md [skip ci] 2020-11-07 12:34:35 +00:00
cff072d1ca Merge pull request #1593 from iluwatar/all-contributors/add-dsibilio
docs: add dsibilio as a contributor
2020-11-07 14:34:08 +02:00
80ba0407db docs: update .all-contributorsrc [skip ci] 2020-11-07 12:33:11 +00:00
6a09b909f2 docs: update README.md [skip ci] 2020-11-07 12:33:10 +00:00
53ccc0e7e6 Merge pull request #1548 from dsibilio/patch-1
Add missing word to README.md
2020-11-07 14:31:26 +02:00
a7a8e23b01 Merge pull request #1591 from iluwatar/all-contributors/add-Ascenio
docs: add Ascenio as a contributor
2020-11-07 09:49:20 +02:00
2783251d00 docs: update .all-contributorsrc [skip ci] 2020-11-07 07:47:42 +00:00
ac432968ae docs: update README.md [skip ci] 2020-11-07 07:47:41 +00:00
26b5364cbd issue 525: attach tutorialspoint link to iterator pattern 2020-10-19 11:24:39 -06:00
f006782805 Merge pull request #1529 from mookkiah/issue_1500
issue 1500 - using JUnit 5 and resolved a build issue
2020-10-17 18:02:56 +03:00
38cc490e3f update namespaces of different steps of build job 2020-10-17 10:14:49 +05:30
911cfd64af Update maven-pr-builder.yml 2020-10-16 09:36:02 +05:30
2332520d67 #1284 Implement Version Number pattern 2020-10-13 20:17:25 +03:00
af1b611136 code refactor 2020-10-13 17:36:59 +02:00
4ff196ce35 Refactor the command pattern to use lambda functions
We can leverage the lambda expressins of Java 8 onwards
to implement command design pattern instead of traditional
non functional way
2020-10-13 16:45:19 +02:00
242ae6a412 #1510 Update class diagram 2020-10-11 00:22:28 +05:30
b689fe0a26 #1510 Fix comment length 2020-10-11 00:11:06 +05:30
7aea765dd1 #1510 Fix review comments 2020-10-10 23:57:53 +05:30
ea49cbfe94 Merge branch 'master' into #1510-Circuit-Breaker-Refactoring 2020-10-10 22:19:46 +05:30
1f4a412e70 Merge pull request #1535 from ohbus/master
Cache SonarCloud packages
2020-10-10 18:51:00 +03:00
36d0a3718c Update README.md
Missing word in sentence.
2020-10-06 18:24:47 +02:00
195a735814 #508 fix SpaceStationMir logging 2020-10-04 14:50:48 +03:00
633d45aa67 Fix typo 2020-10-04 14:33:01 +03:00
adc267e48e Merge pull request #1526 from xiaod-dev/translation-zh
Translation zh
2020-10-04 14:26:39 +03:00
cc8d209c22 Merge pull request #1545 from iluwatar/all-contributors/add-ChFlick
docs: add ChFlick as a contributor
2020-10-04 14:24:48 +03:00
578b3528d5 docs: update .all-contributorsrc [skip ci] 2020-10-04 11:23:50 +00:00
5674f3c52e docs: update README.md [skip ci] 2020-10-04 11:23:49 +00:00
4ad2bfefad Merge pull request #1525 from ChFlick/patch-1
Fix links on the event sourcing page
2020-10-04 14:21:25 +03:00
e5d219609d Add missing license headers 2020-10-04 14:17:28 +03:00
21ca47a22e Fix build 2020-10-04 14:17:10 +03:00
ebd38bcfaa Update license header 2020-10-04 14:09:36 +03:00
a3753807ae add Caching of SonarCloud packages 2020-10-01 22:23:43 +05:30
64266d63fd Merge pull request #1 from iluwatar/master
Update README.md
2020-10-01 22:18:53 +05:30
4f62070eb2 #1510 Revert pom to include all modules 2020-10-01 21:13:30 +05:30
b29bd66369 #1510 Improvments done in Circuit Breaker 2020-10-01 21:09:39 +05:30
ad435dd2fd issue 1500 - using Junit 5 and resolved a build issue 2020-09-27 09:26:19 -04:00
a125879d15 Update README.md 2020-09-26 13:01:58 +03:00
dac8e659ce add facade pattern 2020-09-22 16:50:46 +08:00
a1515b3b52 finish builder and chain pattern 2020-09-22 11:13:25 +08:00
d2e070d21d Fix links on the event sourcing page 2020-09-16 13:44:50 +02:00
82eb41b641 Update README.md 2020-09-13 18:35:23 +03:00
24e8fa1bad Update README.md 2020-09-13 18:32:12 +03:00
9017975276 Update README.md 2020-09-13 18:26:52 +03:00
87093cf221 Update README.md 2020-09-13 18:23:54 +03:00
6cb5b4a683 Update README.md 2020-09-13 18:19:35 +03:00
e6ddff5f25 Update README.md 2020-09-13 18:15:17 +03:00
b5fddd469a Update README.md 2020-09-13 18:09:41 +03:00
9cbc509c3a Update README.md 2020-09-13 18:09:18 +03:00
9c648cbdb8 Update README.md 2020-09-13 18:04:30 +03:00
e6cca86e25 Update README.md 2020-09-13 17:59:12 +03:00
c204b242df Update README.md 2020-09-13 17:53:50 +03:00
2e98dcf217 Update README.md 2020-09-13 17:39:10 +03:00
9d44eea64f Merge pull request #1524 from iluwatar/all-contributors/add-swarajsaaj
docs: add swarajsaaj as a contributor
2020-09-13 17:24:32 +03:00
6f592f5e8a docs: update .all-contributorsrc [skip ci] 2020-09-13 14:23:53 +00:00
74b968942f docs: update README.md [skip ci] 2020-09-13 14:23:52 +00:00
ebc0e8b3cd Merge pull request #1522 from swarajsaaj/master
#1313 Add Separated Interface pattern
2020-09-13 17:21:28 +03:00
9088ac51f6 #1313 Rename DomesticTax,ForeignTax and review fixes 2020-09-12 22:35:40 +05:30
c8f7a8f0e6 Merge pull request #1523 from iluwatar/all-contributors/add-vdlald
docs: add vdlald as a contributor
2020-09-12 20:02:32 +03:00
c63af2ccbf docs: update .all-contributorsrc [skip ci] 2020-09-12 17:00:59 +00:00
9f3f5322d2 docs: update README.md [skip ci] 2020-09-12 17:00:58 +00:00
5607a4974c Merge pull request #1517 from vdlald/847
847
2020-09-12 19:57:29 +03:00
93aa1046aa translate decorator and factory method pattern in Chinese 2020-09-11 09:34:11 +08:00
a2967c5a40 #1313 Add documentation and license header 2020-09-10 03:22:00 +05:30
7fd7735527 #1313 Add separated-interface module to parent pom 2020-09-10 03:10:58 +05:30
f6942cf18d #1313 Add Separated Interface design pattern 2020-09-10 02:57:56 +05:30
ef326ee77e Update README.md 2020-09-06 19:56:07 +03:00
8b5f532a50 Update README.md 2020-09-06 19:55:38 +03:00
a1da1e4973 Cleanup factory 2020-09-06 19:46:13 +03:00
9d21dff855 Merge pull request #1520 from iluwatar/all-contributors/add-ravening
docs: add ravening as a contributor
2020-09-06 19:39:08 +03:00
9d75592e8b Merge branch 'master' into all-contributors/add-ravening 2020-09-06 19:38:44 +03:00
8d6738b729 docs: update .all-contributorsrc [skip ci] 2020-09-06 16:37:04 +00:00
3205dc2cf0 docs: update README.md [skip ci] 2020-09-06 16:37:03 +00:00
16e1863ae7 Merge pull request #1519 from iluwatar/all-contributors/add-samilAyoub
docs: add samilAyoub as a contributor
2020-09-06 19:36:35 +03:00
b9db3c4763 docs: update .all-contributorsrc [skip ci] 2020-09-06 16:35:58 +00:00
d72206ba72 docs: update README.md [skip ci] 2020-09-06 16:35:57 +00:00
922c699e49 Merge pull request #1516 from samilAyoub/add-simple-factory
Add Simple Factory Pattern implementation
2020-09-06 19:33:03 +03:00
bab48efd7c fix style 2020-09-06 12:01:48 +03:00
29eecfd048 forgot to run the App 2020-09-06 11:52:16 +03:00
87cf6b791c refactor 2020-09-06 11:48:40 +03:00
2e36a11e24 remove lombok, related to #1503 2020-09-06 11:42:39 +03:00
bf41b1d9c9 Updates README.md:
- Adding class diagram
- Adding Pros and Cons
- replace "" with ''
2020-09-05 18:39:28 +01:00
b3ef214cd6 Change tabs to spaces in pom.xml 2020-09-04 22:02:19 +01:00
6caf78e4e5 updates :
- Using lambda expression to create cars
- Using spaces instead of tabs in pom.xml
2020-09-04 21:21:51 +01:00
bd48d6ce10 refactor 2020-09-04 17:31:50 +03:00
8b26452c75 bug fixing 2020-09-03 22:58:15 +01:00
2bb252e08f Clean the code 2020-09-03 22:41:55 +01:00
a023cfbb1a Merge branch 'master' into add-simple-factory 2020-09-03 22:26:49 +01:00
badf0c6b8c - README.md is added
- Change the name to factory is done
- Local variable type inference is used
2020-09-03 22:08:54 +01:00
c9718a5227 add README file 2020-09-03 21:08:28 +01:00
e89042a782 remove boilerplate code 2020-09-03 20:04:47 +03:00
fb890e80dd refactor 2020-09-03 20:02:52 +03:00
b423fd30d4 Fix bugs, clean the code and add unit tests. 2020-09-02 18:12:42 +01:00
3df8472bf8 Merge pull request #1515 from fedorskvorcov/fix-typo
Remove unnecessary word from text
2020-09-02 19:59:07 +03:00
ac98b31b68 Add Maven Assembly plugin to pom.xml 2020-09-02 14:09:44 +01:00
46b23f322f Add Simple Factory Pattern implementation
Java source code demonstrate simple factory design pattern
2020-09-02 13:46:53 +01:00
e231cd8d1a Remove unnecessary word from text 2020-09-02 12:32:02 +03:00
19378f3fdd Update README.md 2020-09-01 20:25:39 +03:00
3f4d637510 Update README.md 2020-09-01 20:18:10 +03:00
25cca3547d Update README.md 2020-09-01 20:06:47 +03:00
b9b6777d15 Update README.md 2020-09-01 19:55:22 +03:00
2a5b8c977a Merge pull request #1514 from iluwatar/all-contributors/add-fedorskvorcov
docs: add fedorskvorcov as a contributor
2020-09-01 16:40:23 +03:00
daa94c7b6d docs: update .all-contributorsrc [skip ci] 2020-09-01 13:39:33 +00:00
7aca64a3c9 docs: update README.md [skip ci] 2020-09-01 13:39:32 +00:00
6628bccecc Merge pull request #1513 from fedorskvorcov/fix-typo
Fix typo in comment
2020-09-01 16:38:44 +03:00
aebdb88a83 Fix typo in comment 2020-09-01 09:51:46 +03:00
9c0c17b87a Merge pull request #1512 from xiaod-dev/translation-zh
Translation zh
2020-08-31 20:17:39 +03:00
20fac32ac2 finish Chinese translation of observer and strategy 2020-08-31 17:18:59 +08:00
82842d614b Update README.md 2020-08-30 20:08:34 +03:00
9b71479d04 Update README.md 2020-08-30 19:34:10 +03:00
3c4ae6c4ca Update README.md 2020-08-30 19:17:45 +03:00
9ff42389c6 Merge pull request #1511 from ohbus/master
Configure build to disable shallow clone
2020-08-30 11:52:13 +03:00
b80b9354c6 Update maven-ci.yml 2020-08-30 02:31:06 +05:30
67d1d16e1f Update README.md 2020-08-29 22:13:55 +03:00
bc35911475 Update README.md 2020-08-29 22:02:10 +03:00
b5c6a89ec9 Update README.md 2020-08-29 21:55:51 +03:00
74360a7ecb Update README.md 2020-08-29 21:51:32 +03:00
3544a8366f Update README.md 2020-08-29 21:38:58 +03:00
bcca9beb4d Update README.md 2020-08-29 21:29:15 +03:00
6606d6cd08 Update README.md 2020-08-29 21:21:01 +03:00
f3fd49870c Update README.md 2020-08-29 21:05:30 +03:00
1fbef60f37 Update README.md 2020-08-29 21:00:17 +03:00
b77a05f0fb Update README.md 2020-08-29 20:46:40 +03:00
0ee03db4d0 Update README.md 2020-08-29 20:38:04 +03:00
c541176b38 Update README.md 2020-08-29 20:26:37 +03:00
b53856b64f Merge pull request #1509 from ohbus/master
Cleaning up unnecessary code from the CI yaml and CI server version upgrade
2020-08-29 20:19:42 +03:00
1973d1bc63 Update maven-pr-builder.yml
upgraded build server runtime from Ubuntu 18.04 to 20.04 LTS for the PR builder as well
2020-08-29 19:35:20 +05:30
f5886325ec Update maven-ci.yml
upgraded build server runtime from Ubuntu 18.04 to 20.04 LTS
2020-08-29 19:34:43 +05:30
8afe4c314a Update README.md 2020-08-29 16:56:52 +03:00
2dd2cfb8ca Update README.md 2020-08-29 16:49:45 +03:00
8512c65aef Update README.md 2020-08-29 16:42:46 +03:00
6373f7b115 Update README.md 2020-08-29 16:38:20 +03:00
e8b42bd135 Update README.md 2020-08-29 16:23:28 +03:00
2bb2134636 Update README.md 2020-08-29 16:17:15 +03:00
675b2f14b2 Update README.md 2020-08-29 16:10:59 +03:00
338c146c78 Update maven-pr-builder.yml 2020-08-29 17:39:50 +05:30
8135dbecdb Update maven-ci.yml 2020-08-29 17:36:31 +05:30
a4f2d14848 Update README.md 2020-08-29 12:01:23 +03:00
96c16a8f3a Update README.md 2020-08-29 11:29:30 +03:00
47e746c3ba Update maven-pr-builder.yml
removed the if checking block for building Pull Requests as this was redundant code.
2020-08-28 12:26:27 +05:30
7118ccafa9 Update maven-ci.yml
Removed if clause for building code in main codebase from the CI pipeline.
2020-08-28 12:17:38 +05:30
8983f9c11c Update README.md 2020-08-26 21:55:05 +03:00
9b464e0be1 Merge pull request #1507 from amit1307/upgrade-mockito-1486
Upgrade Mockito version
2020-08-26 21:20:11 +03:00
b07d33f332 Upgrade Mockito version to latest 2020-08-26 00:09:30 +01:00
6c4c6097be Merge branch 'master' of https://github.com/iluwatar/java-design-patterns 2020-08-25 23:21:25 +01:00
9dd46d7b4a Update README.md 2020-08-25 21:42:42 +03:00
723afb85ba Set version for next development iteration 2020-08-25 21:21:36 +03:00
a0e5d061cb Milestone 1.23.0 2020-08-25 21:20:30 +03:00
687648af0a Merge pull request #1506 from iluwatar/all-contributors/add-stefanbirkner
docs: add stefanbirkner as a contributor
2020-08-25 17:43:29 +03:00
96aa21d0e8 docs: update .all-contributorsrc [skip ci] 2020-08-25 14:42:54 +00:00
b8f83c326d docs: update README.md [skip ci] 2020-08-25 14:42:53 +00:00
15d795bf8a Merge pull request #1505 from stefanbirkner/system-lambda
Replace System Rules with System Lambda
2020-08-25 17:41:09 +03:00
3754c66604 Replace System Rules with System Lambda
System Lambda is more specific. It only wraps the part of the code that
produces the output.
2020-08-24 23:20:03 +02:00
6d83ceba28 Update README.md 2020-08-23 18:53:57 +03:00
015b418114 Update README.md 2020-08-23 18:03:29 +03:00
0cba307844 Fix readme filename 2020-08-23 17:06:37 +03:00
a66edc84a0 Merge pull request #1504 from iluwatar/all-contributors/add-mkrzywanski
docs: add mkrzywanski as a contributor
2020-08-23 17:00:32 +03:00
c18282ad5d docs: update .all-contributorsrc [skip ci] 2020-08-23 13:59:15 +00:00
7411ea86bf docs: update README.md [skip ci] 2020-08-23 13:59:14 +00:00
ef033b66a6 Merge pull request #1499 from mkrzywanski/pattern/filterer
Filterer pattern
2020-08-23 16:56:06 +03:00
e65b65257e fixing typos in readme file, introducing var local type inference where possible 2020-08-23 11:00:15 +02:00
3d9afbaeec fixed typo in read me 2020-08-22 18:24:41 +02:00
61a819aab8 Added fixes after review. Changed example pattern application to threat detection domain 2020-08-22 18:11:14 +02:00
61b95c294b Update github token 2020-08-22 14:49:56 +03:00
4068d1fead Update sonar badges 2020-08-22 14:03:21 +03:00
b284230ecf Merge pull request #1502 from iluwatar/all-contributors/add-edycutjong
docs: add edycutjong as a contributor
2020-08-21 18:01:31 +03:00
0529b77abb docs: update .all-contributorsrc [skip ci] 2020-08-21 15:00:49 +00:00
a2ae5d1324 docs: update README.md [skip ci] 2020-08-21 15:00:48 +00:00
25159ed9a8 Merge pull request #1501 from iluwatar/all-contributors/add-ToxicDreamz
docs: add ToxicDreamz as a contributor
2020-08-21 17:35:37 +03:00
905b5dc6d8 Implemented filterer pattern 2020-08-21 11:51:43 +02:00
1e385056fc finish translate adapter pattern into chinese 2020-08-19 17:10:14 +08:00
46d4155328 docs: update .all-contributorsrc [skip ci] 2020-07-29 17:08:13 +00:00
a968dce586 docs: update README.md [skip ci] 2020-07-29 17:08:12 +00:00
9b25d302b7 Fix broken logging in service layer 2020-07-26 21:57:15 +01:00
394 changed files with 12264 additions and 2681 deletions

View File

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"profile": "https://github.com/Anurag870",
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"profile": "https://github.com/grzesiekkedzior",
"contributions": [
"code"
"code",
"review"
]
},
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"profile": "https://github.com/ravening",
"contributions": [
"code"
"code",
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]
},
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"code"
]
},
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"name": "Edy Cu Tjong",
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"profile": "http://www.edycutjong.com",
"contributions": [
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"name": "Michał Krzywański",
"avatar_url": "https://avatars0.githubusercontent.com/u/15279585?v=4",
"profile": "https://github.com/mkrzywanski",
"contributions": [
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{
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View File

@ -30,35 +30,51 @@ on:
push:
branches: [ master ]
jobs:
build:
runs-on: ubuntu-18.04
runs-on: ubuntu-20.04
steps:
- uses: actions/checkout@v2
- name: Checkout Code
uses: actions/checkout@v2
with:
# Disabling shallow clone for improving relevancy of SonarQube reporting
fetch-depth: 0
- name: Set up JDK 11
uses: actions/setup-java@v1
with:
java-version: 11
- uses: actions/cache@v2
- name: Cache SonarCloud packages
uses: actions/cache@v2
with:
path: ~/.sonar/cache
key: ${{ runner.os }}-sonar
restore-keys: ${{ runner.os }}-sonar
- name: Cache Maven dependencies
uses: actions/cache@v2
with:
path: ~/.m2/repository
key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
restore-keys: |
${{ runner.os }}-maven-
# Some tests need screen access
- name: Install xvfb
run: sudo apt-get install xvfb
# SonarQube scan does not work for forked repositories
run: sudo apt-get install -y xvfb
# The SonarQube analysis is only for the master branch of the main repository.
# SonarQube scan does not work for forked repositories try changing it to xvfb-run mvn clean verify
# See https://jira.sonarsource.com/browse/MMF-1371
- name: Build with Maven
if: github.ref != 'refs/heads/master'
run: xvfb-run mvn clean verify
- name: Build with Maven and run SonarQube analysis
if: github.ref == 'refs/heads/master'
run: xvfb-run mvn clean verify org.sonarsource.scanner.maven:sonar-maven-plugin:sonar
env:
# These two env variables are needed for sonar analysis
GITHUB_TOKEN: ${{ secrets.REPOSITORY_ACCESS_TOKEN }}
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

View File

@ -29,29 +29,36 @@ name: Java PR Builder
on:
pull_request:
branches: [ master ]
types: [ opened, reopened, synchronize, labeled, unlabeled ]
jobs:
build:
runs-on: ubuntu-18.04
runs-on: ubuntu-20.04
steps:
- uses: actions/checkout@v2
- name: Checkout Code
uses: actions/checkout@v2
- name: Set up JDK 11
uses: actions/setup-java@v1
with:
java-version: 11
- uses: actions/cache@v2
- name: Cache Maven Dependecies
uses: actions/cache@v2
with:
path: ~/.m2/repository
key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
restore-keys: |
${{ runner.os }}-maven-
# Some tests need screen access
- name: Install xvfb
run: sudo apt-get install xvfb
# SonarQube scan does not work for forked repositories
run: sudo apt-get install -y xvfb
# This worflow is only for building Pull Requests, the master branch runs Sonar analysis on the main repository.
# SonarQube scan does not work for forked repositories.
# See https://jira.sonarsource.com/browse/MMF-1371
- name: Build with Maven
if: github.ref != 'refs/heads/master'
run: xvfb-run mvn clean verify

8
.gitignore vendored
View File

@ -4,7 +4,8 @@ target
.classpath
.project
*.class
# Package Files #
### Package Files ###
*.jar
*.war
*.ear
@ -13,7 +14,8 @@ target
*.swp
datanucleus.log
/bin/
/bin/
/bin/
*.log
event-sourcing/Journal.json
### Checkstyle ###
.checkstyle

305
README.md
View File

@ -6,12 +6,19 @@
![Java CI with Maven](https://github.com/iluwatar/java-design-patterns/workflows/Java%20CI%20with%20Maven/badge.svg)
[![License MIT](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/iluwatar/java-design-patterns/master/LICENSE.md)
[![Lines of Code](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=ncloc)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
[![Coverage](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=coverage)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
[![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
[![Sonarcloud Status](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=alert_status)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
[![All Contributors](https://img.shields.io/badge/all_contributors-126-orange.svg?style=flat-square)](#contributors-)
[![All Contributors](https://img.shields.io/badge/all_contributors-151-orange.svg?style=flat-square)](#contributors-)
<!-- ALL-CONTRIBUTORS-BADGE:END -->
<br/>
Read in different language : [![CN](/assets/flags/CN.png)**CN**](/zh/README.md),[![KR](/assets/flags/KR.png)**KR**](/ko/README.md),[![FR](/assets/flags/FR.png)**FR**](/fr/README.md),[![TR](/assets/flags/TR.png)**TR**](/tr/README.md),
<br/>
# Introduction
Design patterns are the best formalized practices a programmer can use to
@ -30,7 +37,7 @@ This site showcases Java Design Patterns. The solutions have been developed by
experienced programmers and architects from the open source community. The
patterns can be browsed by their high level descriptions or by looking at their
source code. The source code examples are well commented and can be thought as
programming tutorials how to implement a specific pattern. We use the most
programming tutorials on how to implement a specific pattern. We use the most
popular battle-proven open source Java technologies.
Before you dive into the material, you should be familiar with various
@ -69,197 +76,235 @@ This project is licensed under the terms of the MIT license.
<!-- markdownlint-disable -->
<table>
<tr>
<td align="center"><a href="https://github.com/iluwatar"><img src="https://avatars1.githubusercontent.com/u/582346?v=4" width="100px;" alt=""/><br /><sub><b>Ilkka Seppälä</b></sub></a><br /><a href="#projectManagement-iluwatar" title="Project Management">📆</a> <a href="#maintenance-iluwatar" title="Maintenance">🚧</a> <a href="#content-iluwatar" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/amit1307"><img src="https://avatars0.githubusercontent.com/u/23420222?v=4" width="100px;" alt=""/><br /><sub><b>amit1307</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit1307" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/npathai"><img src="https://avatars2.githubusercontent.com/u/1792515?v=4" width="100px;" alt=""/><br /><sub><b>Narendra Pathai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npathai" title="Code">💻</a> <a href="#ideas-npathai" title="Ideas, Planning, & Feedback">🤔</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Anpathai" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://github.com/fluxw42"><img src="https://avatars1.githubusercontent.com/u/1545460?v=4" width="100px;" alt=""/><br /><sub><b>Jeroen Meulemeester</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fluxw42" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/iluwatar"><img src="https://avatars1.githubusercontent.com/u/582346?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ilkka Seppälä</b></sub></a><br /><a href="#projectManagement-iluwatar" title="Project Management">📆</a> <a href="#maintenance-iluwatar" title="Maintenance">🚧</a> <a href="#content-iluwatar" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/amit1307"><img src="https://avatars0.githubusercontent.com/u/23420222?v=4?s=100" width="100px;" alt=""/><br /><sub><b>amit1307</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit1307" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/npathai"><img src="https://avatars2.githubusercontent.com/u/1792515?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Narendra Pathai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npathai" title="Code">💻</a> <a href="#ideas-npathai" title="Ideas, Planning, & Feedback">🤔</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Anpathai" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://github.com/fluxw42"><img src="https://avatars1.githubusercontent.com/u/1545460?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jeroen Meulemeester</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fluxw42" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="http://www.joemccarthy.co.uk"><img src="https://avatars0.githubusercontent.com/u/4526195?v=4" width="100px;" alt=""/><br /><sub><b>Joseph McCarthy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mikulucky" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/thomasoss"><img src="https://avatars1.githubusercontent.com/u/22516154?v=4" width="100px;" alt=""/><br /><sub><b>Thomas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=thomasoss" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/anuragagarwal561994"><img src="https://avatars1.githubusercontent.com/u/6075379?v=4" width="100px;" alt=""/><br /><sub><b>Anurag Agarwal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anuragagarwal561994" title="Code">💻</a></td>
<td align="center"><a href="https://markusmo3.github.io"><img src="https://avatars1.githubusercontent.com/u/3317416?v=4" width="100px;" alt=""/><br /><sub><b>Markus Moser</b></sub></a><br /><a href="#design-markusmo3" title="Design">🎨</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=markusmo3" title="Code">💻</a> <a href="#ideas-markusmo3" title="Ideas, Planning, & Feedback">🤔</a></td>
<td align="center"><a href="http://www.joemccarthy.co.uk"><img src="https://avatars0.githubusercontent.com/u/4526195?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Joseph McCarthy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mikulucky" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/thomasoss"><img src="https://avatars1.githubusercontent.com/u/22516154?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Thomas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=thomasoss" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/anuragagarwal561994"><img src="https://avatars1.githubusercontent.com/u/6075379?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Anurag Agarwal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anuragagarwal561994" title="Code">💻</a></td>
<td align="center"><a href="https://markusmo3.github.io"><img src="https://avatars1.githubusercontent.com/u/3317416?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Markus Moser</b></sub></a><br /><a href="#design-markusmo3" title="Design">🎨</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=markusmo3" title="Code">💻</a> <a href="#ideas-markusmo3" title="Ideas, Planning, & Feedback">🤔</a></td>
</tr>
<tr>
<td align="center"><a href="https://twitter.com/i_sabiq"><img src="https://avatars1.githubusercontent.com/u/19510920?v=4" width="100px;" alt=""/><br /><sub><b>Sabiq Ihab</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=isabiq" title="Code">💻</a></td>
<td align="center"><a href="http://inbravo.github.io"><img src="https://avatars3.githubusercontent.com/u/5253764?v=4" width="100px;" alt=""/><br /><sub><b>Amit Dixit</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=inbravo" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/piyushchaudhari04"><img src="https://avatars3.githubusercontent.com/u/10268029?v=4" width="100px;" alt=""/><br /><sub><b>Piyush Kailash Chaudhari</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=piyushchaudhari04" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/joshzambales"><img src="https://avatars1.githubusercontent.com/u/8704552?v=4" width="100px;" alt=""/><br /><sub><b>joshzambales</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joshzambales" title="Code">💻</a></td>
<td align="center"><a href="https://twitter.com/i_sabiq"><img src="https://avatars1.githubusercontent.com/u/19510920?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sabiq Ihab</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=isabiq" title="Code">💻</a></td>
<td align="center"><a href="http://inbravo.github.io"><img src="https://avatars3.githubusercontent.com/u/5253764?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Amit Dixit</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=inbravo" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/piyushchaudhari04"><img src="https://avatars3.githubusercontent.com/u/10268029?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Piyush Kailash Chaudhari</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=piyushchaudhari04" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/joshzambales"><img src="https://avatars1.githubusercontent.com/u/8704552?v=4?s=100" width="100px;" alt=""/><br /><sub><b>joshzambales</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joshzambales" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/Crossy147"><img src="https://avatars2.githubusercontent.com/u/7272996?v=4" width="100px;" alt=""/><br /><sub><b>Kamil Pietruszka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Crossy147" title="Code">💻</a></td>
<td align="center"><a href="http://cs.joensuu.fi/~zkhayda"><img src="https://avatars2.githubusercontent.com/u/660742?v=4" width="100px;" alt=""/><br /><sub><b>Zafar Khaydarov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Documentation">📖</a></td>
<td align="center"><a href="https://kemitix.github.io/"><img src="https://avatars1.githubusercontent.com/u/1147749?v=4" width="100px;" alt=""/><br /><sub><b>Paul Campbell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kemitix" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Argyro-Sioziou"><img src="https://avatars0.githubusercontent.com/u/22822639?v=4" width="100px;" alt=""/><br /><sub><b>Argyro Sioziou</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Argyro-Sioziou" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Crossy147"><img src="https://avatars2.githubusercontent.com/u/7272996?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kamil Pietruszka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Crossy147" title="Code">💻</a></td>
<td align="center"><a href="http://cs.joensuu.fi/~zkhayda"><img src="https://avatars2.githubusercontent.com/u/660742?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Zafar Khaydarov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=zafarella" title="Documentation">📖</a></td>
<td align="center"><a href="https://kemitix.github.io/"><img src="https://avatars1.githubusercontent.com/u/1147749?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Paul Campbell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kemitix" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Argyro-Sioziou"><img src="https://avatars0.githubusercontent.com/u/22822639?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Argyro Sioziou</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Argyro-Sioziou" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/TylerMcConville"><img src="https://avatars0.githubusercontent.com/u/4946449?v=4" width="100px;" alt=""/><br /><sub><b>TylerMcConville</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=TylerMcConville" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/saksham93"><img src="https://avatars1.githubusercontent.com/u/37399540?v=4" width="100px;" alt=""/><br /><sub><b>saksham93</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=saksham93" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/nikhilbarar"><img src="https://avatars2.githubusercontent.com/u/37332144?v=4" width="100px;" alt=""/><br /><sub><b>nikhilbarar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nikhilbarar" title="Code">💻</a></td>
<td align="center"><a href="http://colinbut.com"><img src="https://avatars2.githubusercontent.com/u/10725674?v=4" width="100px;" alt=""/><br /><sub><b>Colin But</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=colinbut" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/TylerMcConville"><img src="https://avatars0.githubusercontent.com/u/4946449?v=4?s=100" width="100px;" alt=""/><br /><sub><b>TylerMcConville</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=TylerMcConville" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/saksham93"><img src="https://avatars1.githubusercontent.com/u/37399540?v=4?s=100" width="100px;" alt=""/><br /><sub><b>saksham93</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=saksham93" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/nikhilbarar"><img src="https://avatars2.githubusercontent.com/u/37332144?v=4?s=100" width="100px;" alt=""/><br /><sub><b>nikhilbarar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nikhilbarar" title="Code">💻</a></td>
<td align="center"><a href="http://colinbut.com"><img src="https://avatars2.githubusercontent.com/u/10725674?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Colin But</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=colinbut" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/ruslanpa"><img src="https://avatars2.githubusercontent.com/u/1503411?v=4" width="100px;" alt=""/><br /><sub><b>Ruslan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ruslanpa" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/JuhoKang"><img src="https://avatars1.githubusercontent.com/u/4745294?v=4" width="100px;" alt=""/><br /><sub><b>Juho Kang</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=JuhoKang" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/dheeraj-mummareddy"><img src="https://avatars2.githubusercontent.com/u/7002230?v=4" width="100px;" alt=""/><br /><sub><b>Dheeraj Mummareddy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dheeraj-mummareddy" title="Code">💻</a></td>
<td align="center"><a href="https://www.bernardosulzbach.com"><img src="https://avatars0.githubusercontent.com/u/8271090?v=4" width="100px;" alt=""/><br /><sub><b>Bernardo Sulzbach</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=bernardosulzbach" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ruslanpa"><img src="https://avatars2.githubusercontent.com/u/1503411?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ruslan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ruslanpa" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/JuhoKang"><img src="https://avatars1.githubusercontent.com/u/4745294?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Juho Kang</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=JuhoKang" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/dheeraj-mummareddy"><img src="https://avatars2.githubusercontent.com/u/7002230?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dheeraj Mummareddy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dheeraj-mummareddy" title="Code">💻</a></td>
<td align="center"><a href="https://www.bernardosulzbach.com"><img src="https://avatars0.githubusercontent.com/u/8271090?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Bernardo Sulzbach</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=bernardosulzbach" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/4lexis"><img src="https://avatars0.githubusercontent.com/u/19871727?v=4" width="100px;" alt=""/><br /><sub><b>Aleksandar Dudukovic</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=4lexis" title="Code">💻</a></td>
<td align="center"><a href="https://www.yusufaytas.com"><img src="https://avatars2.githubusercontent.com/u/1049483?v=4" width="100px;" alt=""/><br /><sub><b>Yusuf Aytaş</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yusufaytas" title="Code">💻</a></td>
<td align="center"><a href="http://futurehomes.hu"><img src="https://avatars2.githubusercontent.com/u/1001491?v=4" width="100px;" alt=""/><br /><sub><b>Mihály Kuprivecz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qpi" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/kapinuss"><img src="https://avatars0.githubusercontent.com/u/17639945?v=4" width="100px;" alt=""/><br /><sub><b>Stanislav Kapinus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kapinuss" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/4lexis"><img src="https://avatars0.githubusercontent.com/u/19871727?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Aleksandar Dudukovic</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=4lexis" title="Code">💻</a></td>
<td align="center"><a href="https://www.yusufaytas.com"><img src="https://avatars2.githubusercontent.com/u/1049483?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yusuf Aytaş</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yusufaytas" title="Code">💻</a></td>
<td align="center"><a href="http://futurehomes.hu"><img src="https://avatars2.githubusercontent.com/u/1001491?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mihály Kuprivecz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qpi" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/kapinuss"><img src="https://avatars0.githubusercontent.com/u/17639945?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Stanislav Kapinus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kapinuss" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/gvsharma"><img src="https://avatars1.githubusercontent.com/u/6648152?v=4" width="100px;" alt=""/><br /><sub><b>GVSharma</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gvsharma" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/SrdjanPaunovic"><img src="https://avatars1.githubusercontent.com/u/22815104?v=4" width="100px;" alt=""/><br /><sub><b>Srđan Paunović</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=SrdjanPaunovic" title="Code">💻</a></td>
<td align="center"><a href="https://sideris.xyz/"><img src="https://avatars3.githubusercontent.com/u/5484694?v=4" width="100px;" alt=""/><br /><sub><b>Petros G. Sideris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sideris" title="Code">💻</a></td>
<td align="center"><a href="https://www.linkedin.com/in/pramodgupta3/"><img src="https://avatars1.githubusercontent.com/u/2184241?v=4" width="100px;" alt=""/><br /><sub><b>Pramod Gupta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AIAmPramod" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://github.com/gvsharma"><img src="https://avatars1.githubusercontent.com/u/6648152?v=4?s=100" width="100px;" alt=""/><br /><sub><b>GVSharma</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gvsharma" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/SrdjanPaunovic"><img src="https://avatars1.githubusercontent.com/u/22815104?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Srđan Paunović</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=SrdjanPaunovic" title="Code">💻</a></td>
<td align="center"><a href="https://sideris.xyz/"><img src="https://avatars3.githubusercontent.com/u/5484694?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Petros G. Sideris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sideris" title="Code">💻</a></td>
<td align="center"><a href="https://www.linkedin.com/in/pramodgupta3/"><img src="https://avatars1.githubusercontent.com/u/2184241?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Pramod Gupta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AIAmPramod" title="Reviewed Pull Requests">👀</a></td>
</tr>
<tr>
<td align="center"><a href="https://amarnath510.github.io/portfolio"><img src="https://avatars0.githubusercontent.com/u/4599623?v=4" width="100px;" alt=""/><br /><sub><b>Amarnath Chandana</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Amarnath510" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Anurag870"><img src="https://avatars1.githubusercontent.com/u/6295975?v=4" width="100px;" alt=""/><br /><sub><b>Anurag870</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Anurag870" title="Code">💻</a></td>
<td align="center"><a href="http://theerroris.me"><img src="https://avatars0.githubusercontent.com/u/1685953?v=4" width="100px;" alt=""/><br /><sub><b>Wes Gilleland</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Deathnerd" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Harshrajsinh"><img src="https://avatars2.githubusercontent.com/u/22811531?v=4" width="100px;" alt=""/><br /><sub><b>Harshraj Thakor</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Harshrajsinh" title="Code">💻</a></td>
<td align="center"><a href="https://amarnath510.github.io/portfolio"><img src="https://avatars0.githubusercontent.com/u/4599623?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Amarnath Chandana</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Amarnath510" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Anurag870"><img src="https://avatars1.githubusercontent.com/u/6295975?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Anurag870</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Anurag870" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=Anurag870" title="Documentation">📖</a></td>
<td align="center"><a href="http://theerroris.me"><img src="https://avatars0.githubusercontent.com/u/1685953?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Wes Gilleland</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Deathnerd" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Harshrajsinh"><img src="https://avatars2.githubusercontent.com/u/22811531?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Harshraj Thakor</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Harshrajsinh" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/MaVdbussche"><img src="https://avatars1.githubusercontent.com/u/26136934?v=4" width="100px;" alt=""/><br /><sub><b>Martin Vandenbussche</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MaVdbussche" title="Code">💻</a></td>
<td align="center"><a href="https://alexsomai.com"><img src="https://avatars1.githubusercontent.com/u/5720977?v=4" width="100px;" alt=""/><br /><sub><b>Alexandru Somai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=alexsomai" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/amogozov"><img src="https://avatars3.githubusercontent.com/u/7372215?v=4" width="100px;" alt=""/><br /><sub><b>Artur Mogozov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amogozov" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/anthonycampbell"><img src="https://avatars3.githubusercontent.com/u/10249255?v=4" width="100px;" alt=""/><br /><sub><b>anthony</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anthonycampbell" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/MaVdbussche"><img src="https://avatars1.githubusercontent.com/u/26136934?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Martin Vandenbussche</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MaVdbussche" title="Code">💻</a></td>
<td align="center"><a href="https://alexsomai.com"><img src="https://avatars1.githubusercontent.com/u/5720977?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Alexandru Somai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=alexsomai" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/amogozov"><img src="https://avatars3.githubusercontent.com/u/7372215?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Artur Mogozov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amogozov" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/anthonycampbell"><img src="https://avatars3.githubusercontent.com/u/10249255?v=4?s=100" width="100px;" alt=""/><br /><sub><b>anthony</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=anthonycampbell" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="http://ccygnus.com/"><img src="https://avatars1.githubusercontent.com/u/9342724?v=4" width="100px;" alt=""/><br /><sub><b>Christian Cygnus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christophercolumbusdog" title="Code">💻</a></td>
<td align="center"><a href="https://about.me/dzmitryh"><img src="https://avatars2.githubusercontent.com/u/5390492?v=4" width="100px;" alt=""/><br /><sub><b>Dima Gubin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dzmitryh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/jjjimenez100"><img src="https://avatars3.githubusercontent.com/u/22243493?v=4" width="100px;" alt=""/><br /><sub><b>Joshua Jimenez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jjjimenez100" title="Code">💻</a></td>
<td align="center"><a href="http://about.me/kaiwinter"><img src="https://avatars0.githubusercontent.com/u/110982?v=4" width="100px;" alt=""/><br /><sub><b>Kai Winter</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kaiwinter" title="Code">💻</a></td>
<td align="center"><a href="http://ccygnus.com/"><img src="https://avatars1.githubusercontent.com/u/9342724?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christian Cygnus</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christophercolumbusdog" title="Code">💻</a></td>
<td align="center"><a href="https://about.me/dzmitryh"><img src="https://avatars2.githubusercontent.com/u/5390492?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dima Gubin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dzmitryh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/jjjimenez100"><img src="https://avatars3.githubusercontent.com/u/22243493?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Joshua Jimenez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jjjimenez100" title="Code">💻</a></td>
<td align="center"><a href="http://about.me/kaiwinter"><img src="https://avatars0.githubusercontent.com/u/110982?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kai Winter</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kaiwinter" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/lbroman"><img src="https://avatars1.githubusercontent.com/u/86007?v=4" width="100px;" alt=""/><br /><sub><b>lbroman</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=lbroman" title="Code">💻</a></td>
<td align="center"><a href="https://przemeknowak.com"><img src="https://avatars1.githubusercontent.com/u/3254609?v=4" width="100px;" alt=""/><br /><sub><b>Przemek</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pnowy" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/prafful1"><img src="https://avatars0.githubusercontent.com/u/14350274?v=4" width="100px;" alt=""/><br /><sub><b>Prafful Agarwal</b></sub></a><br /><a href="#content-prafful1" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/sankypanhale"><img src="https://avatars1.githubusercontent.com/u/6478783?v=4" width="100px;" alt=""/><br /><sub><b>Sanket Panhale</b></sub></a><br /><a href="#content-sankypanhale" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/lbroman"><img src="https://avatars1.githubusercontent.com/u/86007?v=4?s=100" width="100px;" alt=""/><br /><sub><b>lbroman</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=lbroman" title="Code">💻</a></td>
<td align="center"><a href="https://przemeknowak.com"><img src="https://avatars1.githubusercontent.com/u/3254609?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Przemek</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pnowy" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/prafful1"><img src="https://avatars0.githubusercontent.com/u/14350274?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Prafful Agarwal</b></sub></a><br /><a href="#content-prafful1" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/sankypanhale"><img src="https://avatars1.githubusercontent.com/u/6478783?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sanket Panhale</b></sub></a><br /><a href="#content-sankypanhale" title="Content">🖋</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/staillebois"><img src="https://avatars0.githubusercontent.com/u/23701200?v=4" width="100px;" alt=""/><br /><sub><b>staillebois</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=staillebois" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/valdar-hu"><img src="https://avatars3.githubusercontent.com/u/17962817?v=4" width="100px;" alt=""/><br /><sub><b>Krisztián Nagy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=valdar-hu" title="Code">💻</a></td>
<td align="center"><a href="https://www.vanogrid.com"><img src="https://avatars0.githubusercontent.com/u/4307918?v=4" width="100px;" alt=""/><br /><sub><b>Alexander Ivanov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vanogrid" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/yosfik"><img src="https://avatars3.githubusercontent.com/u/4850270?v=4" width="100px;" alt=""/><br /><sub><b>Yosfik Alqadri</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yosfik" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/staillebois"><img src="https://avatars0.githubusercontent.com/u/23701200?v=4?s=100" width="100px;" alt=""/><br /><sub><b>staillebois</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=staillebois" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/valdar-hu"><img src="https://avatars3.githubusercontent.com/u/17962817?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Krisztián Nagy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=valdar-hu" title="Code">💻</a></td>
<td align="center"><a href="https://www.vanogrid.com"><img src="https://avatars0.githubusercontent.com/u/4307918?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Alexander Ivanov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vanogrid" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/yosfik"><img src="https://avatars3.githubusercontent.com/u/4850270?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yosfik Alqadri</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yosfik" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/7agustibm"><img src="https://avatars0.githubusercontent.com/u/8149332?v=4" width="100px;" alt=""/><br /><sub><b>Agustí Becerra Milà</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=7agustibm" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Juaanma"><img src="https://avatars3.githubusercontent.com/u/7390500?v=4" width="100px;" alt=""/><br /><sub><b>Juan Manuel Suárez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Juaanma" title="Code">💻</a></td>
<td align="center"><a href="http://www.devsedge.net/"><img src="https://avatars0.githubusercontent.com/u/9956006?v=4" width="100px;" alt=""/><br /><sub><b>Luigi Cortese</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=LuigiCortese" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Rzeposlaw"><img src="https://avatars2.githubusercontent.com/u/18425745?v=4" width="100px;" alt=""/><br /><sub><b>Katarzyna Rzepecka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Rzeposlaw" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/7agustibm"><img src="https://avatars0.githubusercontent.com/u/8149332?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Agustí Becerra Milà</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=7agustibm" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Juaanma"><img src="https://avatars3.githubusercontent.com/u/7390500?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Juan Manuel Suárez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Juaanma" title="Code">💻</a></td>
<td align="center"><a href="http://www.devsedge.net/"><img src="https://avatars0.githubusercontent.com/u/9956006?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Luigi Cortese</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=LuigiCortese" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Rzeposlaw"><img src="https://avatars2.githubusercontent.com/u/18425745?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Katarzyna Rzepecka</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Rzeposlaw" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="http://adamski.pro"><img src="https://avatars1.githubusercontent.com/u/6537430?v=4" width="100px;" alt=""/><br /><sub><b>adamski.pro</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=akrystian" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/baislsl"><img src="https://avatars0.githubusercontent.com/u/17060584?v=4" width="100px;" alt=""/><br /><sub><b>Shengli Bai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=baislsl" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/besok"><img src="https://avatars2.githubusercontent.com/u/29834592?v=4" width="100px;" alt=""/><br /><sub><b>Boris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=besok" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/dmitraver"><img src="https://avatars3.githubusercontent.com/u/1798156?v=4" width="100px;" alt=""/><br /><sub><b>Dmitry Avershin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dmitraver" title="Code">💻</a></td>
<td align="center"><a href="http://adamski.pro"><img src="https://avatars1.githubusercontent.com/u/6537430?v=4?s=100" width="100px;" alt=""/><br /><sub><b>adamski.pro</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=akrystian" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/baislsl"><img src="https://avatars0.githubusercontent.com/u/17060584?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Shengli Bai</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=baislsl" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/besok"><img src="https://avatars2.githubusercontent.com/u/29834592?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Boris</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=besok" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/dmitraver"><img src="https://avatars3.githubusercontent.com/u/1798156?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dmitry Avershin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dmitraver" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/fanofxiaofeng"><img src="https://avatars0.githubusercontent.com/u/3983683?v=4" width="100px;" alt=""/><br /><sub><b>靳阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fanofxiaofeng" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/hoangnam2261"><img src="https://avatars2.githubusercontent.com/u/31692990?v=4" width="100px;" alt=""/><br /><sub><b>hoangnam2261</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoangnam2261" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/jarpit96"><img src="https://avatars2.githubusercontent.com/u/10098713?v=4" width="100px;" alt=""/><br /><sub><b>Arpit Jain</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jarpit96" title="Code">💻</a></td>
<td align="center"><a href="http://joningi.net"><img src="https://avatars2.githubusercontent.com/u/6115148?v=4" width="100px;" alt=""/><br /><sub><b>Jón Ingi Sveinbjörnsson</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joningiwork" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/fanofxiaofeng"><img src="https://avatars0.githubusercontent.com/u/3983683?v=4?s=100" width="100px;" alt=""/><br /><sub><b>靳阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fanofxiaofeng" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/hoangnam2261"><img src="https://avatars2.githubusercontent.com/u/31692990?v=4?s=100" width="100px;" alt=""/><br /><sub><b>hoangnam2261</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoangnam2261" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/jarpit96"><img src="https://avatars2.githubusercontent.com/u/10098713?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Arpit Jain</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jarpit96" title="Code">💻</a></td>
<td align="center"><a href="http://joningi.net"><img src="https://avatars2.githubusercontent.com/u/6115148?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jón Ingi Sveinbjörnsson</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=joningiwork" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/kirill-vlasov"><img src="https://avatars3.githubusercontent.com/u/16112495?v=4" width="100px;" alt=""/><br /><sub><b>Kirill Vlasov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kirill-vlasov" title="Code">💻</a></td>
<td align="center"><a href="http://mitchell-irvin.com"><img src="https://avatars0.githubusercontent.com/u/16233245?v=4" width="100px;" alt=""/><br /><sub><b>Mitchell Irvin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mitchellirvin" title="Code">💻</a></td>
<td align="center"><a href="https://ranjeet-floyd.github.io"><img src="https://avatars0.githubusercontent.com/u/1992972?v=4" width="100px;" alt=""/><br /><sub><b>Ranjeet</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ranjeet-floyd" title="Code">💻</a></td>
<td align="center"><a href="https://alwayswithme.github.io"><img src="https://avatars3.githubusercontent.com/u/3234786?v=4" width="100px;" alt=""/><br /><sub><b>PhoenixYip</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Alwayswithme" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/kirill-vlasov"><img src="https://avatars3.githubusercontent.com/u/16112495?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kirill Vlasov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kirill-vlasov" title="Code">💻</a></td>
<td align="center"><a href="http://mitchell-irvin.com"><img src="https://avatars0.githubusercontent.com/u/16233245?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mitchell Irvin</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mitchellirvin" title="Code">💻</a></td>
<td align="center"><a href="https://ranjeet-floyd.github.io"><img src="https://avatars0.githubusercontent.com/u/1992972?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ranjeet</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ranjeet-floyd" title="Code">💻</a></td>
<td align="center"><a href="https://alwayswithme.github.io"><img src="https://avatars3.githubusercontent.com/u/3234786?v=4?s=100" width="100px;" alt=""/><br /><sub><b>PhoenixYip</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Alwayswithme" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/MSaifAsif"><img src="https://avatars1.githubusercontent.com/u/6280554?v=4" width="100px;" alt=""/><br /><sub><b>M Saif Asif</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MSaifAsif" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/kanwarpreet25"><img src="https://avatars0.githubusercontent.com/u/39183641?v=4" width="100px;" alt=""/><br /><sub><b>kanwarpreet25</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kanwarpreet25" title="Code">💻</a></td>
<td align="center"><a href="http://leonmak.me"><img src="https://avatars3.githubusercontent.com/u/13071508?v=4" width="100px;" alt=""/><br /><sub><b>Leon Mak</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leonmak" title="Code">💻</a></td>
<td align="center"><a href="http://www.wramdemark.se"><img src="https://avatars2.githubusercontent.com/u/7052193?v=4" width="100px;" alt=""/><br /><sub><b>Per Wramdemark</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=perwramdemark" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/MSaifAsif"><img src="https://avatars1.githubusercontent.com/u/6280554?v=4?s=100" width="100px;" alt=""/><br /><sub><b>M Saif Asif</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=MSaifAsif" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/kanwarpreet25"><img src="https://avatars0.githubusercontent.com/u/39183641?v=4?s=100" width="100px;" alt=""/><br /><sub><b>kanwarpreet25</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=kanwarpreet25" title="Code">💻</a></td>
<td align="center"><a href="http://leonmak.me"><img src="https://avatars3.githubusercontent.com/u/13071508?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Leon Mak</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leonmak" title="Code">💻</a></td>
<td align="center"><a href="http://www.wramdemark.se"><img src="https://avatars2.githubusercontent.com/u/7052193?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Per Wramdemark</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=perwramdemark" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/waisuan"><img src="https://avatars2.githubusercontent.com/u/10975700?v=4" width="100px;" alt=""/><br /><sub><b>Evan Sia Wai Suan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=waisuan" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/AnaghaSasikumar"><img src="https://avatars2.githubusercontent.com/u/42939261?v=4" width="100px;" alt=""/><br /><sub><b>AnaghaSasikumar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=AnaghaSasikumar" title="Code">💻</a></td>
<td align="center"><a href="https://christofferh.com"><img src="https://avatars1.githubusercontent.com/u/767643?v=4" width="100px;" alt=""/><br /><sub><b>Christoffer Hamberg</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christofferh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/dgruntz"><img src="https://avatars0.githubusercontent.com/u/1516800?v=4" width="100px;" alt=""/><br /><sub><b>Dominik Gruntz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dgruntz" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/waisuan"><img src="https://avatars2.githubusercontent.com/u/10975700?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Evan Sia Wai Suan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=waisuan" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/AnaghaSasikumar"><img src="https://avatars2.githubusercontent.com/u/42939261?v=4?s=100" width="100px;" alt=""/><br /><sub><b>AnaghaSasikumar</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=AnaghaSasikumar" title="Code">💻</a></td>
<td align="center"><a href="https://christofferh.com"><img src="https://avatars1.githubusercontent.com/u/767643?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christoffer Hamberg</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=christofferh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/dgruntz"><img src="https://avatars0.githubusercontent.com/u/1516800?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dominik Gruntz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dgruntz" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://bitbucket.org/hannespernpeintner/"><img src="https://avatars3.githubusercontent.com/u/1679437?v=4" width="100px;" alt=""/><br /><sub><b>Hannes</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hannespernpeintner" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/leogtzr"><img src="https://avatars0.githubusercontent.com/u/1211969?v=4" width="100px;" alt=""/><br /><sub><b>Leo Gutiérrez Ramírez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leogtzr" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/npczwh"><img src="https://avatars0.githubusercontent.com/u/14066422?v=4" width="100px;" alt=""/><br /><sub><b>Zhang WH</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npczwh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/oconnelc"><img src="https://avatars0.githubusercontent.com/u/1112973?v=4" width="100px;" alt=""/><br /><sub><b>Christopher O'Connell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=oconnelc" title="Code">💻</a></td>
<td align="center"><a href="https://bitbucket.org/hannespernpeintner/"><img src="https://avatars3.githubusercontent.com/u/1679437?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Hannes</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hannespernpeintner" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/leogtzr"><img src="https://avatars0.githubusercontent.com/u/1211969?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Leo Gutiérrez Ramírez</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=leogtzr" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/npczwh"><img src="https://avatars0.githubusercontent.com/u/14066422?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Zhang WH</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=npczwh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/oconnelc"><img src="https://avatars0.githubusercontent.com/u/1112973?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christopher O'Connell</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=oconnelc" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/giorgosmav21"><img src="https://avatars2.githubusercontent.com/u/22855493?v=4" width="100px;" alt=""/><br /><sub><b>George Mavroeidis</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=giorgosmav21" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/hbothra15"><img src="https://avatars1.githubusercontent.com/u/7418012?v=4" width="100px;" alt=""/><br /><sub><b>Hemant Bothra</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hbothra15" title="Code">💻</a> <a href="#design-hbothra15" title="Design">🎨</a></td>
<td align="center"><a href="https://www.kevinpeters.net/about/"><img src="https://avatars1.githubusercontent.com/u/12736734?v=4" width="100px;" alt=""/><br /><sub><b>Kevin Peters</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=igeligel" title="Code">💻</a></td>
<td align="center"><a href="https://llorllale.github.io/"><img src="https://avatars1.githubusercontent.com/u/2019896?v=4" width="100px;" alt=""/><br /><sub><b>George Aristy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=llorllale" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/giorgosmav21"><img src="https://avatars2.githubusercontent.com/u/22855493?v=4?s=100" width="100px;" alt=""/><br /><sub><b>George Mavroeidis</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=giorgosmav21" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/hbothra15"><img src="https://avatars1.githubusercontent.com/u/7418012?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Hemant Bothra</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hbothra15" title="Code">💻</a> <a href="#design-hbothra15" title="Design">🎨</a></td>
<td align="center"><a href="https://www.kevinpeters.net/about/"><img src="https://avatars1.githubusercontent.com/u/12736734?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kevin Peters</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=igeligel" title="Code">💻</a></td>
<td align="center"><a href="https://llorllale.github.io/"><img src="https://avatars1.githubusercontent.com/u/2019896?v=4?s=100" width="100px;" alt=""/><br /><sub><b>George Aristy</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=llorllale" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/mookkiah"><img src="https://avatars1.githubusercontent.com/u/8975264?v=4" width="100px;" alt=""/><br /><sub><b>Mahendran Mookkiah</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mookkiah" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Azureyjt"><img src="https://avatars2.githubusercontent.com/u/18476317?v=4" width="100px;" alt=""/><br /><sub><b>Azureyjt</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Azureyjt" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/vehpsr"><img src="https://avatars2.githubusercontent.com/u/3133265?v=4" width="100px;" alt=""/><br /><sub><b>gans</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vehpsr" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ThatGuyWithTheHat"><img src="https://avatars0.githubusercontent.com/u/24470582?v=4" width="100px;" alt=""/><br /><sub><b>Matt</b></sub></a><br /><a href="#content-ThatGuyWithTheHat" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/mookkiah"><img src="https://avatars1.githubusercontent.com/u/8975264?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mahendran Mookkiah</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mookkiah" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Azureyjt"><img src="https://avatars2.githubusercontent.com/u/18476317?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Azureyjt</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Azureyjt" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/vehpsr"><img src="https://avatars2.githubusercontent.com/u/3133265?v=4?s=100" width="100px;" alt=""/><br /><sub><b>gans</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vehpsr" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ThatGuyWithTheHat"><img src="https://avatars0.githubusercontent.com/u/24470582?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Matt</b></sub></a><br /><a href="#content-ThatGuyWithTheHat" title="Content">🖋</a></td>
</tr>
<tr>
<td align="center"><a href="https://www.linkedin.com/in/gopinathlangote/"><img src="https://avatars2.githubusercontent.com/u/10210778?v=4" width="100px;" alt=""/><br /><sub><b>Gopinath Langote</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gopinath-langote" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/hoswey"><img src="https://avatars3.githubusercontent.com/u/3689445?v=4" width="100px;" alt=""/><br /><sub><b>Hoswey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoswey" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/amit2103"><img src="https://avatars3.githubusercontent.com/u/7566692?v=4" width="100px;" alt=""/><br /><sub><b>Amit Pandey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit2103" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/gwildor28"><img src="https://avatars0.githubusercontent.com/u/16000365?v=4" width="100px;" alt=""/><br /><sub><b>gwildor28</b></sub></a><br /><a href="#content-gwildor28" title="Content">🖋</a></td>
<td align="center"><a href="https://www.linkedin.com/in/gopinathlangote/"><img src="https://avatars2.githubusercontent.com/u/10210778?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Gopinath Langote</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gopinath-langote" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/hoswey"><img src="https://avatars3.githubusercontent.com/u/3689445?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Hoswey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=hoswey" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/amit2103"><img src="https://avatars3.githubusercontent.com/u/7566692?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Amit Pandey</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=amit2103" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/gwildor28"><img src="https://avatars0.githubusercontent.com/u/16000365?v=4?s=100" width="100px;" alt=""/><br /><sub><b>gwildor28</b></sub></a><br /><a href="#content-gwildor28" title="Content">🖋</a></td>
</tr>
<tr>
<td align="center"><a href="https://t.me/paul_docker"><img src="https://avatars1.githubusercontent.com/u/2404785?v=4" width="100px;" alt=""/><br /><sub><b>田浩</b></sub></a><br /><a href="#content-llitfkitfk" title="Content">🖋</a></td>
<td align="center"><a href="https://twitter.com/StPitsios"><img src="https://avatars1.githubusercontent.com/u/6773603?v=4" width="100px;" alt=""/><br /><sub><b>Stamatis Pitsios</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pitsios-s" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/qza"><img src="https://avatars3.githubusercontent.com/u/233149?v=4" width="100px;" alt=""/><br /><sub><b>qza</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qza" title="Code">💻</a></td>
<td align="center"><a href="http://tschis.github.io"><img src="https://avatars1.githubusercontent.com/u/20662669?v=4" width="100px;" alt=""/><br /><sub><b>Rodolfo Forte</b></sub></a><br /><a href="#content-Tschis" title="Content">🖋</a></td>
<td align="center"><a href="https://t.me/paul_docker"><img src="https://avatars1.githubusercontent.com/u/2404785?v=4?s=100" width="100px;" alt=""/><br /><sub><b>田浩</b></sub></a><br /><a href="#content-llitfkitfk" title="Content">🖋</a></td>
<td align="center"><a href="https://twitter.com/StPitsios"><img src="https://avatars1.githubusercontent.com/u/6773603?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Stamatis Pitsios</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=pitsios-s" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/qza"><img src="https://avatars3.githubusercontent.com/u/233149?v=4?s=100" width="100px;" alt=""/><br /><sub><b>qza</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qza" title="Code">💻</a></td>
<td align="center"><a href="http://tschis.github.io"><img src="https://avatars1.githubusercontent.com/u/20662669?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rodolfo Forte</b></sub></a><br /><a href="#content-Tschis" title="Content">🖋</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/ankurkaushal"><img src="https://avatars2.githubusercontent.com/u/2236616?v=4" width="100px;" alt=""/><br /><sub><b>Ankur Kaushal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ankurkaushal" title="Code">💻</a></td>
<td align="center"><a href="https://www.linkedin.com/in/ovidijus-okinskas/"><img src="https://avatars0.githubusercontent.com/u/20372387?v=4" width="100px;" alt=""/><br /><sub><b>Ovidijus Okinskas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=okinskas" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/robertt240"><img src="https://avatars1.githubusercontent.com/u/9137432?v=4" width="100px;" alt=""/><br /><sub><b>Robert Kasperczyk</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=robertt240" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/trautonen"><img src="https://avatars3.githubusercontent.com/u/1641063?v=4" width="100px;" alt=""/><br /><sub><b>Tapio Rautonen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=trautonen" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ankurkaushal"><img src="https://avatars2.githubusercontent.com/u/2236616?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ankur Kaushal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ankurkaushal" title="Code">💻</a></td>
<td align="center"><a href="https://www.linkedin.com/in/ovidijus-okinskas/"><img src="https://avatars0.githubusercontent.com/u/20372387?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ovidijus Okinskas</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=okinskas" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/robertt240"><img src="https://avatars1.githubusercontent.com/u/9137432?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Robert Kasperczyk</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=robertt240" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/trautonen"><img src="https://avatars3.githubusercontent.com/u/1641063?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Tapio Rautonen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=trautonen" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="http://vk.com/yuri.orlov"><img src="https://avatars0.githubusercontent.com/u/1595733?v=4" width="100px;" alt=""/><br /><sub><b>Yuri Orlov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yorlov" title="Code">💻</a></td>
<td align="center"><a href="https://www.linkedin.com/in/varunu28/"><img src="https://avatars0.githubusercontent.com/u/7676016?v=4" width="100px;" alt=""/><br /><sub><b>Varun Upadhyay</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=varunu28" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/PalAditya"><img src="https://avatars2.githubusercontent.com/u/25523604?v=4" width="100px;" alt=""/><br /><sub><b>Aditya Pal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=PalAditya" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/grzesiekkedzior"><img src="https://avatars3.githubusercontent.com/u/23739158?v=4" width="100px;" alt=""/><br /><sub><b>grzesiekkedzior</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=grzesiekkedzior" title="Code">💻</a></td>
<td align="center"><a href="http://vk.com/yuri.orlov"><img src="https://avatars0.githubusercontent.com/u/1595733?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yuri Orlov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yorlov" title="Code">💻</a></td>
<td align="center"><a href="https://www.linkedin.com/in/varunu28/"><img src="https://avatars0.githubusercontent.com/u/7676016?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Varun Upadhyay</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=varunu28" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/PalAditya"><img src="https://avatars2.githubusercontent.com/u/25523604?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Aditya Pal</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=PalAditya" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/grzesiekkedzior"><img src="https://avatars3.githubusercontent.com/u/23739158?v=4?s=100" width="100px;" alt=""/><br /><sub><b>grzesiekkedzior</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=grzesiekkedzior" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Agrzesiekkedzior" title="Reviewed Pull Requests">👀</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/sivasubramanim"><img src="https://avatars2.githubusercontent.com/u/51107434?v=4" width="100px;" alt=""/><br /><sub><b>Sivasubramani M</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sivasubramanim" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/d4gg4d"><img src="https://avatars2.githubusercontent.com/u/99457?v=4" width="100px;" alt=""/><br /><sub><b>Sami Airaksinen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=d4gg4d" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/vertti"><img src="https://avatars0.githubusercontent.com/u/557751?v=4" width="100px;" alt=""/><br /><sub><b>Janne Sinivirta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vertti" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Bobo1239"><img src="https://avatars1.githubusercontent.com/u/2302947?v=4" width="100px;" alt=""/><br /><sub><b>Boris-Chengbiao Zhou</b></sub></a><br /><a href="#content-Bobo1239" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/sivasubramanim"><img src="https://avatars2.githubusercontent.com/u/51107434?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sivasubramani M</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=sivasubramanim" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/d4gg4d"><img src="https://avatars2.githubusercontent.com/u/99457?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sami Airaksinen</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=d4gg4d" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/vertti"><img src="https://avatars0.githubusercontent.com/u/557751?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Janne Sinivirta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vertti" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Bobo1239"><img src="https://avatars1.githubusercontent.com/u/2302947?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Boris-Chengbiao Zhou</b></sub></a><br /><a href="#content-Bobo1239" title="Content">🖋</a></td>
</tr>
<tr>
<td align="center"><a href="https://jahhein.github.io"><img src="https://avatars2.githubusercontent.com/u/10779515?v=4" width="100px;" alt=""/><br /><sub><b>Jacob Hein</b></sub></a><br /><a href="#content-Jahhein" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/iamrichardjones"><img src="https://avatars3.githubusercontent.com/u/14842151?v=4" width="100px;" alt=""/><br /><sub><b>Richard Jones</b></sub></a><br /><a href="#content-iamrichardjones" title="Content">🖋</a></td>
<td align="center"><a href="https://rachelcarmena.github.io"><img src="https://avatars0.githubusercontent.com/u/22792183?v=4" width="100px;" alt=""/><br /><sub><b>Rachel M. Carmena</b></sub></a><br /><a href="#content-rachelcarmena" title="Content">🖋</a></td>
<td align="center"><a href="https://zd-zero.github.io"><img src="https://avatars0.githubusercontent.com/u/21978370?v=4" width="100px;" alt=""/><br /><sub><b>Zaerald Denze Lungos</b></sub></a><br /><a href="#content-zd-zero" title="Content">🖋</a></td>
<td align="center"><a href="https://jahhein.github.io"><img src="https://avatars2.githubusercontent.com/u/10779515?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jacob Hein</b></sub></a><br /><a href="#content-Jahhein" title="Content">🖋</a></td>
<td align="center"><a href="https://github.com/iamrichardjones"><img src="https://avatars3.githubusercontent.com/u/14842151?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Richard Jones</b></sub></a><br /><a href="#content-iamrichardjones" title="Content">🖋</a></td>
<td align="center"><a href="https://rachelcarmena.github.io"><img src="https://avatars0.githubusercontent.com/u/22792183?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rachel M. Carmena</b></sub></a><br /><a href="#content-rachelcarmena" title="Content">🖋</a></td>
<td align="center"><a href="https://zd-zero.github.io"><img src="https://avatars0.githubusercontent.com/u/21978370?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Zaerald Denze Lungos</b></sub></a><br /><a href="#content-zd-zero" title="Content">🖋</a></td>
</tr>
<tr>
<td align="center"><a href="https://webpro.nl"><img src="https://avatars1.githubusercontent.com/u/456426?v=4" width="100px;" alt=""/><br /><sub><b>Lars Kappert</b></sub></a><br /><a href="#content-webpro" title="Content">🖋</a></td>
<td align="center"><a href="https://xiaod.info"><img src="https://avatars2.githubusercontent.com/u/21277644?v=4" width="100px;" alt=""/><br /><sub><b>Mike Liu</b></sub></a><br /><a href="#translation-xiaod-dev" title="Translation">🌍</a></td>
<td align="center"><a href="https://github.com/charlesfinley"><img src="https://avatars1.githubusercontent.com/u/6307904?v=4" width="100px;" alt=""/><br /><sub><b>Matt Dolan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=charlesfinley" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Acharlesfinley" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://github.com/MananS77"><img src="https://avatars3.githubusercontent.com/u/21033516?v=4" width="100px;" alt=""/><br /><sub><b>Manan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AMananS77" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://webpro.nl"><img src="https://avatars1.githubusercontent.com/u/456426?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Lars Kappert</b></sub></a><br /><a href="#content-webpro" title="Content">🖋</a></td>
<td align="center"><a href="https://xiaod.info"><img src="https://avatars2.githubusercontent.com/u/21277644?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mike Liu</b></sub></a><br /><a href="#translation-xiaod-dev" title="Translation">🌍</a></td>
<td align="center"><a href="https://github.com/charlesfinley"><img src="https://avatars1.githubusercontent.com/u/6307904?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Matt Dolan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=charlesfinley" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Acharlesfinley" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://github.com/MananS77"><img src="https://avatars3.githubusercontent.com/u/21033516?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Manan</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AMananS77" title="Reviewed Pull Requests">👀</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/nishant"><img src="https://avatars2.githubusercontent.com/u/15331971?v=4" width="100px;" alt=""/><br /><sub><b>Nishant Arora</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nishant" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/raja-peeyush-kumar-singh"><img src="https://avatars0.githubusercontent.com/u/5496024?v=4" width="100px;" alt=""/><br /><sub><b>Peeyush</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=raja-peeyush-kumar-singh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ravening"><img src="https://avatars1.githubusercontent.com/u/10645273?v=4" width="100px;" alt=""/><br /><sub><b>Rakesh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ravening" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/vINCENT8888801"><img src="https://avatars0.githubusercontent.com/u/8037883?v=4" width="100px;" alt=""/><br /><sub><b>Wei Seng</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vINCENT8888801" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/nishant"><img src="https://avatars2.githubusercontent.com/u/15331971?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Nishant Arora</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nishant" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/raja-peeyush-kumar-singh"><img src="https://avatars0.githubusercontent.com/u/5496024?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Peeyush</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=raja-peeyush-kumar-singh" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ravening"><img src="https://avatars1.githubusercontent.com/u/10645273?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rakesh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ravening" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aravening" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://github.com/vINCENT8888801"><img src="https://avatars0.githubusercontent.com/u/8037883?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Wei Seng</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vINCENT8888801" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://www.linkedin.com/in/ashish-trivedi-218379135/"><img src="https://avatars3.githubusercontent.com/u/23194128?v=4" width="100px;" alt=""/><br /><sub><b>Ashish Trivedi</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ashishtrivedi16" title="Code">💻</a></td>
<td align="center"><a href="https://rayyounghong.com"><img src="https://avatars1.githubusercontent.com/u/41055099?v=4" width="100px;" alt=""/><br /><sub><b>洪月阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=RayYH" title="Code">💻</a></td>
<td align="center"><a href="https://xdvrx1.github.io/"><img src="https://avatars0.githubusercontent.com/u/47092464?v=4" width="100px;" alt=""/><br /><sub><b>xdvrx1</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Axdvrx1" title="Reviewed Pull Requests">👀</a> <a href="#ideas-xdvrx1" title="Ideas, Planning, & Feedback">🤔</a></td>
<td align="center"><a href="http://subho.xyz"><img src="https://avatars0.githubusercontent.com/u/13291222?v=4" width="100px;" alt=""/><br /><sub><b>Subhrodip Mohanta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ohbus" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aohbus" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://www.linkedin.com/in/ashish-trivedi-218379135/"><img src="https://avatars3.githubusercontent.com/u/23194128?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ashish Trivedi</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ashishtrivedi16" title="Code">💻</a></td>
<td align="center"><a href="https://rayyounghong.com"><img src="https://avatars1.githubusercontent.com/u/41055099?v=4?s=100" width="100px;" alt=""/><br /><sub><b>洪月阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=RayYH" title="Code">💻</a></td>
<td align="center"><a href="https://xdvrx1.github.io/"><img src="https://avatars0.githubusercontent.com/u/47092464?v=4?s=100" width="100px;" alt=""/><br /><sub><b>xdvrx1</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Axdvrx1" title="Reviewed Pull Requests">👀</a> <a href="#ideas-xdvrx1" title="Ideas, Planning, & Feedback">🤔</a></td>
<td align="center"><a href="http://subho.xyz"><img src="https://avatars0.githubusercontent.com/u/13291222?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Subhrodip Mohanta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ohbus" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aohbus" title="Reviewed Pull Requests">👀</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/nahteb"><img src="https://avatars3.githubusercontent.com/u/13121570?v=4" width="100px;" alt=""/><br /><sub><b>Bethan Palmer</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nahteb" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ToxicDreamz"><img src="https://avatars0.githubusercontent.com/u/45225562?v=4" width="100px;" alt=""/><br /><sub><b>Toxic Dreamz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ToxicDreamz" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/nahteb"><img src="https://avatars3.githubusercontent.com/u/13121570?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Bethan Palmer</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nahteb" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ToxicDreamz"><img src="https://avatars0.githubusercontent.com/u/45225562?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Toxic Dreamz</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ToxicDreamz" title="Code">💻</a></td>
<td align="center"><a href="http://www.edycutjong.com"><img src="https://avatars1.githubusercontent.com/u/1098102?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Edy Cu Tjong</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=edycutjong" title="Documentation">📖</a></td>
<td align="center"><a href="https://github.com/mkrzywanski"><img src="https://avatars0.githubusercontent.com/u/15279585?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Michał Krzywański</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=mkrzywanski" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://www.stefan-birkner.de"><img src="https://avatars1.githubusercontent.com/u/711349?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Stefan Birkner</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=stefanbirkner" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/fedorskvorcov"><img src="https://avatars3.githubusercontent.com/u/43882212?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Fedor Skvorcov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=fedorskvorcov" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/samilAyoub"><img src="https://avatars0.githubusercontent.com/u/61546990?v=4?s=100" width="100px;" alt=""/><br /><sub><b>samilAyoub</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=samilAyoub" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/vdlald"><img src="https://avatars0.githubusercontent.com/u/29997701?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Vladislav Golubinov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=vdlald" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/swarajsaaj"><img src="https://avatars2.githubusercontent.com/u/6285049?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Swaraj</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=swarajsaaj" title="Code">💻</a></td>
<td align="center"><a href="http://christophflick.de"><img src="https://avatars0.githubusercontent.com/u/4465376?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christoph Flick</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ChFlick" title="Documentation">📖</a></td>
<td align="center"><a href="https://github.com/Ascenio"><img src="https://avatars1.githubusercontent.com/u/7662016?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ascênio</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AAscenio" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://www.linkedin.com/in/domenico-sibilio/"><img src="https://avatars2.githubusercontent.com/u/24280982?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Domenico Sibilio</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=dsibilio" title="Documentation">📖</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/akashchandwani"><img src="https://avatars2.githubusercontent.com/u/3483277?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Akash Chandwani</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aakashchandwani" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="http://www.linkedin.com/in/manannikov"><img src="https://avatars2.githubusercontent.com/u/7019769?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Pavlo Manannikov</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=manannikov" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/eimanip"><img src="https://avatars0.githubusercontent.com/u/20307301?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Eiman</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=eimanip" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/OrangePants-R"><img src="https://avatars0.githubusercontent.com/u/42976136?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rocky</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=OrangePants-R" title="Documentation">📖</a></td>
</tr>
<tr>
<td align="center"><a href="https://ibrahimalii.github.io/"><img src="https://avatars2.githubusercontent.com/u/21141301?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ibrahim ali abdelghany</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3AibrahimAlii" title="Reviewed Pull Requests">👀</a></td>
<td align="center"><a href="https://github.com/gkulkarni2020"><img src="https://avatars3.githubusercontent.com/u/5161548?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Girish Kulkarni</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=gkulkarni2020" title="Documentation">📖</a></td>
<td align="center"><a href="https://github.com/omk13"><img src="https://avatars0.githubusercontent.com/u/59054172?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Omar Karazoun</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=omk13" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/jeff303"><img src="https://avatars0.githubusercontent.com/u/3521562?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jeff Evans</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=jeff303" title="Code">💻</a></td>
</tr>
<tr>
<td align="center"><a href="https://viveksb007.github.io"><img src="https://avatars1.githubusercontent.com/u/12713808?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Vivek Singh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=viveksb007" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/siavashsoleymani"><img src="https://avatars2.githubusercontent.com/u/18074419?v=4?s=100" width="100px;" alt=""/><br /><sub><b>siavash</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=siavashsoleymani" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/ruchpeanuts"><img src="https://avatars0.githubusercontent.com/u/29301900?v=4?s=100" width="100px;" alt=""/><br /><sub><b>ruchpeanuts</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ruchpeanuts" title="Documentation">📖</a></td>
<td align="center"><a href="https://github.com/warp125"><img src="https://avatars1.githubusercontent.com/u/48073115?v=4?s=100" width="100px;" alt=""/><br /><sub><b>warp125</b></sub></a><br /><a href="#translation-warp125" title="Translation">🌍</a></td>
</tr>
<tr>
<td align="center"><a href="http://libkhadir.fr"><img src="https://avatars1.githubusercontent.com/u/45130488?v=4?s=100" width="100px;" alt=""/><br /><sub><b>KHADIR Tayeb</b></sub></a><br /><a href="#translation-tkhadir" title="Translation">🌍</a></td>
<td align="center"><a href="https://github.com/ignite1771"><img src="https://avatars2.githubusercontent.com/u/59446563?v=4?s=100" width="100px;" alt=""/><br /><sub><b>ignite1771</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ignite1771" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/demirhalil"><img src="https://avatars1.githubusercontent.com/u/22895118?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Halil Demir</b></sub></a><br /><a href="#translation-demirhalil" title="Translation">🌍</a></td>
</tr>
</table>
<!-- markdownlint-enable -->
<!-- markdownlint-restore -->
<!-- prettier-ignore-end -->
<!-- ALL-CONTRIBUTORS-LIST:END -->

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@ -21,7 +21,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>abstract-document</artifactId>
<dependencies>

View File

@ -22,7 +22,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>abstract-factory</artifactId>
<dependencies>

View File

@ -23,7 +23,6 @@
package com.iluwatar.abstractfactory;
import com.iluwatar.abstractfactory.App.FactoryMaker.KingdomType;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@ -41,84 +40,14 @@ import org.slf4j.LoggerFactory;
* and its implementations ( {@link ElfKingdomFactory}, {@link OrcKingdomFactory}). The example uses
* both concrete implementations to create a king, a castle and an army.
*/
public class App {
public class App implements Runnable {
private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
private static Logger log = LoggerFactory.getLogger(App.class);
private King king;
private Castle castle;
private Army army;
private final Kingdom kingdom = new Kingdom();
/**
* Creates kingdom.
*/
public void createKingdom(final KingdomFactory factory) {
setKing(factory.createKing());
setCastle(factory.createCastle());
setArmy(factory.createArmy());
}
King getKing(final KingdomFactory factory) {
return factory.createKing();
}
public King getKing() {
return king;
}
private void setKing(final King king) {
this.king = king;
}
Castle getCastle(final KingdomFactory factory) {
return factory.createCastle();
}
public Castle getCastle() {
return castle;
}
private void setCastle(final Castle castle) {
this.castle = castle;
}
Army getArmy(final KingdomFactory factory) {
return factory.createArmy();
}
public Army getArmy() {
return army;
}
private void setArmy(final Army army) {
this.army = army;
}
/**
* The factory of kingdom factories.
*/
public static class FactoryMaker {
/**
* Enumeration for the different types of Kingdoms.
*/
public enum KingdomType {
ELF, ORC
}
/**
* The factory method to create KingdomFactory concrete objects.
*/
public static KingdomFactory makeFactory(KingdomType type) {
switch (type) {
case ELF:
return new ElfKingdomFactory();
case ORC:
return new OrcKingdomFactory();
default:
throw new IllegalArgumentException("KingdomType not supported.");
}
}
public Kingdom getKingdom() {
return kingdom;
}
/**
@ -127,19 +56,33 @@ public class App {
* @param args command line args
*/
public static void main(String[] args) {
var app = new App();
app.run();
}
LOGGER.info("Elf Kingdom");
app.createKingdom(FactoryMaker.makeFactory(KingdomType.ELF));
LOGGER.info(app.getArmy().getDescription());
LOGGER.info(app.getCastle().getDescription());
LOGGER.info(app.getKing().getDescription());
@Override
public void run() {
log.info("Elf Kingdom");
createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
log.info(kingdom.getArmy().getDescription());
log.info(kingdom.getCastle().getDescription());
log.info(kingdom.getKing().getDescription());
LOGGER.info("Orc Kingdom");
app.createKingdom(FactoryMaker.makeFactory(KingdomType.ORC));
LOGGER.info(app.getArmy().getDescription());
LOGGER.info(app.getCastle().getDescription());
LOGGER.info(app.getKing().getDescription());
log.info("Orc Kingdom");
createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
log.info(kingdom.getArmy().getDescription());
log.info(kingdom.getCastle().getDescription());
log.info(kingdom.getKing().getDescription());
}
/**
* Creates kingdom.
* @param kingdomType type of Kingdom
*/
public void createKingdom(final Kingdom.FactoryMaker.KingdomType kingdomType) {
final KingdomFactory kingdomFactory = Kingdom.FactoryMaker.makeFactory(kingdomType);
kingdom.setKing(kingdomFactory.createKing());
kingdom.setCastle(kingdomFactory.createCastle());
kingdom.setArmy(kingdomFactory.createArmy());
}
}

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@ -0,0 +1,82 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
public class Kingdom {
private King king;
private Castle castle;
private Army army;
public King getKing() {
return king;
}
public Castle getCastle() {
return castle;
}
public Army getArmy() {
return army;
}
public void setKing(King king) {
this.king = king;
}
public void setCastle(Castle castle) {
this.castle = castle;
}
public void setArmy(Army army) {
this.army = army;
}
/**
* The factory of kingdom factories.
*/
public static class FactoryMaker {
/**
* Enumeration for the different types of Kingdoms.
*/
public enum KingdomType {
ELF, ORC
}
/**
* The factory method to create KingdomFactory concrete objects.
*/
public static KingdomFactory makeFactory(KingdomType type) {
switch (type) {
case ELF:
return new ElfKingdomFactory();
case ORC:
return new OrcKingdomFactory();
default:
throw new IllegalArgumentException("KingdomType not supported.");
}
}
}
}

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@ -23,65 +23,71 @@
package com.iluwatar.abstractfactory;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;
import com.iluwatar.abstractfactory.App.FactoryMaker;
import com.iluwatar.abstractfactory.App.FactoryMaker.KingdomType;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
/**
* Test for abstract factory.
*/
public class AbstractFactoryTest {
private final App app = new App();
private KingdomFactory elfFactory;
private KingdomFactory orcFactory;
@BeforeEach
public void setUp() {
elfFactory = FactoryMaker.makeFactory(KingdomType.ELF);
orcFactory = FactoryMaker.makeFactory(KingdomType.ORC);
}
@Test
public void king() {
final var elfKing = app.getKing(elfFactory);
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
final var kingdom = app.getKingdom();
final var elfKing = kingdom.getKing();
assertTrue(elfKing instanceof ElfKing);
assertEquals(ElfKing.DESCRIPTION, elfKing.getDescription());
final var orcKing = app.getKing(orcFactory);
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
final var orcKing = kingdom.getKing();
assertTrue(orcKing instanceof OrcKing);
assertEquals(OrcKing.DESCRIPTION, orcKing.getDescription());
}
@Test
public void castle() {
final var elfCastle = app.getCastle(elfFactory);
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
final var kingdom = app.getKingdom();
final var elfCastle = kingdom.getCastle();
assertTrue(elfCastle instanceof ElfCastle);
assertEquals(ElfCastle.DESCRIPTION, elfCastle.getDescription());
final var orcCastle = app.getCastle(orcFactory);
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
final var orcCastle = kingdom.getCastle();
assertTrue(orcCastle instanceof OrcCastle);
assertEquals(OrcCastle.DESCRIPTION, orcCastle.getDescription());
}
@Test
public void army() {
final var elfArmy = app.getArmy(elfFactory);
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
final var kingdom = app.getKingdom();
final var elfArmy = kingdom.getArmy();
assertTrue(elfArmy instanceof ElfArmy);
assertEquals(ElfArmy.DESCRIPTION, elfArmy.getDescription());
final var orcArmy = app.getArmy(orcFactory);
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
final var orcArmy = kingdom.getArmy();
assertTrue(orcArmy instanceof OrcArmy);
assertEquals(OrcArmy.DESCRIPTION, orcArmy.getDescription());
}
@Test
public void createElfKingdom() {
app.createKingdom(elfFactory);
final var king = app.getKing();
final var castle = app.getCastle();
final var army = app.getArmy();
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
final var kingdom = app.getKingdom();
final var king = kingdom.getKing();
final var castle = kingdom.getCastle();
final var army = kingdom.getArmy();
assertTrue(king instanceof ElfKing);
assertEquals(ElfKing.DESCRIPTION, king.getDescription());
assertTrue(castle instanceof ElfCastle);
@ -92,10 +98,12 @@ public class AbstractFactoryTest {
@Test
public void createOrcKingdom() {
app.createKingdom(orcFactory);
final var king = app.getKing();
final var castle = app.getCastle();
final var army = app.getArmy();
app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
final var kingdom = app.getKingdom();
final var king = kingdom.getKing();
final var castle = kingdom.getCastle();
final var army = kingdom.getArmy();
assertTrue(king instanceof OrcKing);
assertEquals(OrcKing.DESCRIPTION, king.getDescription());
assertTrue(castle instanceof OrcCastle);

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@ -21,7 +21,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>acyclic-visitor</artifactId>

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@ -22,7 +22,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>adapter</artifactId>
<dependencies>

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@ -20,7 +20,7 @@
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>aggregator-service</artifactId>

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@ -20,7 +20,7 @@
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -20,7 +20,7 @@
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>inventory-microservice</artifactId>

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@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>aggregator-microservices</artifactId>

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@ -20,7 +20,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>ambassador</artifactId>

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@ -29,7 +29,7 @@
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>api-gateway-service</artifactId>

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@ -29,7 +29,7 @@
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>image-microservice</artifactId>

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@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>api-gateway</artifactId>

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@ -29,7 +29,7 @@
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

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@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

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@ -22,7 +22,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>async-method-invocation</artifactId>
<dependencies>

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@ -20,7 +20,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

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@ -9,20 +9,26 @@ tags:
---
## Also known as
Handle/Body
## Intent
Decouple an abstraction from its implementation so that the two can vary independently.
## Explanation
Real world example
> Consider you have a weapon with different enchantments and you are supposed to allow mixing different weapons with different enchantments. What would you do? Create multiple copies of each of the weapons for each of the enchantments or would you just create separate enchantment and set it for the weapon as needed? Bridge pattern allows you to do the second.
> Consider you have a weapon with different enchantments, and you are supposed to allow mixing
> different weapons with different enchantments. What would you do? Create multiple copies of each
> of the weapons for each of the enchantments or would you just create separate enchantment and set
> it for the weapon as needed? Bridge pattern allows you to do the second.
In Plain Words
> Bridge pattern is about preferring composition over inheritance. Implementation details are pushed from a hierarchy to another object with a separate hierarchy.
> Bridge pattern is about preferring composition over inheritance. Implementation details are pushed
> from a hierarchy to another object with a separate hierarchy.
Wikipedia says
@ -30,7 +36,7 @@ Wikipedia says
**Programmatic Example**
Translating our weapon example from above. Here we have the `Weapon` hierarchy
Translating our weapon example from above. Here we have the `Weapon` hierarchy:
```java
public interface Weapon {
@ -105,7 +111,7 @@ public class Hammer implements Weapon {
}
```
And the separate enchantment hierarchy
Here's the separate enchantment hierarchy:
```java
public interface Enchantment {
@ -151,7 +157,7 @@ public class SoulEatingEnchantment implements Enchantment {
}
```
And both the hierarchies in action
Here are both hierarchies in action:
```java
var enchantedSword = new Sword(new SoulEatingEnchantment());
@ -178,18 +184,21 @@ hammer.unwield();
```
## Class diagram
![alt text](./etc/bridge.urm.png "Bridge class diagram")
## Applicability
Use the Bridge pattern when
* you want to avoid a permanent binding between an abstraction and its implementation. This might be the case, for example, when the implementation must be selected or switched at run-time.
* both the abstractions and their implementations should be extensible by subclassing. In this case, the Bridge pattern lets you combine the different abstractions and implementations and extend them independently
* changes in the implementation of an abstraction should have no impact on clients; that is, their code should not have to be recompiled.
* you have a proliferation of classes. Such a class hierarchy indicates the need for splitting an object into two parts. Rumbaugh uses the term "nested generalizations" to refer to such class hierarchies
* you want to share an implementation among multiple objects (perhaps using reference counting), and this fact should be hidden from the client. A simple example is Coplien's String class, in which multiple objects can share the same string representation.
* You want to avoid a permanent binding between an abstraction and its implementation. This might be the case, for example, when the implementation must be selected or switched at run-time.
* Both the abstractions and their implementations should be extensible by subclassing. In this case, the Bridge pattern lets you combine the different abstractions and implementations and extend them independently.
* Changes in the implementation of an abstraction should have no impact on clients; that is, their code should not have to be recompiled.
* You have a proliferation of classes. Such a class hierarchy indicates the need for splitting an object into two parts. Rumbaugh uses the term "nested generalizations" to refer to such class hierarchies.
* You want to share an implementation among multiple objects (perhaps using reference counting), and this fact should be hidden from the client. A simple example is Coplien's String class, in which multiple objects can share the same string representation.
## Tutorial
* [Bridge Pattern Tutorial](https://www.journaldev.com/1491/bridge-design-pattern-java)
## Credits

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@ -22,7 +22,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>bridge</artifactId>
<dependencies>

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@ -9,36 +9,47 @@ tags:
---
## Intent
Separate the construction of a complex object from its
representation so that the same construction process can create different
representations.
Separate the construction of a complex object from its representation so that the same construction
process can create different representations.
## Explanation
Real world example
> Imagine a character generator for a role playing game. The easiest option is to let computer create the character for you. But if you want to select the character details like profession, gender, hair color etc. the character generation becomes a step-by-step process that completes when all the selections are ready.
> Imagine a character generator for a role-playing game. The easiest option is to let the computer
> create the character for you. If you want to manually select the character details like
> profession, gender, hair color etc. the character generation becomes a step-by-step process that
> completes when all the selections are ready.
In plain words
> Allows you to create different flavors of an object while avoiding constructor pollution. Useful when there could be several flavors of an object. Or when there are a lot of steps involved in creation of an object.
> Allows you to create different flavors of an object while avoiding constructor pollution. Useful
> when there could be several flavors of an object. Or when there are a lot of steps involved in
> creation of an object.
Wikipedia says
> The builder pattern is an object creation software design pattern with the intentions of finding a solution to the telescoping constructor anti-pattern.
> The builder pattern is an object creation software design pattern with the intentions of finding
> a solution to the telescoping constructor anti-pattern.
Having said that let me add a bit about what telescoping constructor anti-pattern is. At one point or the other we have all seen a constructor like below:
Having said that let me add a bit about what telescoping constructor anti-pattern is. At one point
or the other, we have all seen a constructor like below:
```java
public Hero(Profession profession, String name, HairType hairType, HairColor hairColor, Armor armor, Weapon weapon) {
}
```
As you can see the number of constructor parameters can quickly get out of hand and it might become difficult to understand the arrangement of parameters. Plus this parameter list could keep on growing if you would want to add more options in future. This is called telescoping constructor anti-pattern.
As you can see the number of constructor parameters can quickly get out of hand, and it may become
difficult to understand the arrangement of parameters. Plus this parameter list could keep on
growing if you would want to add more options in the future. This is called telescoping constructor
anti-pattern.
**Programmatic Example**
The sane alternative is to use the Builder pattern. First of all we have our hero that we want to create
The sane alternative is to use the Builder pattern. First of all we have our hero that we want to
create:
```java
public final class Hero {
@ -60,7 +71,7 @@ public final class Hero {
}
```
And then we have the builder
Then we have the builder:
```java
public static class Builder {
@ -105,20 +116,22 @@ And then we have the builder
}
```
And then it can be used as:
Then it can be used as:
```java
var mage = new Hero.Builder(Profession.MAGE, "Riobard").withHairColor(HairColor.BLACK).withWeapon(Weapon.DAGGER).build();
```
## Class diagram
![alt text](./etc/builder.urm.png "Builder class diagram")
## Applicability
Use the Builder pattern when
* the algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled
* the construction process must allow different representations for the object that's constructed
* The algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled
* The construction process must allow different representations for the object that's constructed
## Real world examples

View File

@ -22,7 +22,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>builder</artifactId>
<dependencies>

View File

@ -22,7 +22,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>business-delegate</artifactId>
<dependencies>

View File

@ -20,7 +20,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>caching</artifactId>
<dependencies>

View File

@ -9,14 +9,16 @@ tags:
---
## Intent
Callback is a piece of executable code that is passed as an argument to other code, which is expected to call back
(execute) the argument at some convenient time.
Callback is a piece of executable code that is passed as an argument to other code, which is
expected to call back (execute) the argument at some convenient time.
## Explanation
Real world example
> We need to be notified after executing task has finished. We pass a callback method for the executor and wait for it to call back on us.
> We need to be notified after executing task has finished. We pass a callback method for
> the executor and wait for it to call back on us.
In plain words
@ -24,7 +26,9 @@ In plain words
Wikipedia says
> In computer programming, a callback, also known as a "call-after" function, is any executable code that is passed as an argument to other code; that other code is expected to call back (execute) the argument at a given time.
> In computer programming, a callback, also known as a "call-after" function, is any executable
> code that is passed as an argument to other code; that other code is expected to call
> back (execute) the argument at a given time.
**Programmatic Example**
@ -61,7 +65,7 @@ public final class SimpleTask extends Task {
}
```
Finally here's how we execute a task and receive a callback when it's finished.
Finally, here's how we execute a task and receive a callback when it's finished.
```java
var task = new SimpleTask();
@ -69,13 +73,15 @@ Finally here's how we execute a task and receive a callback when it's finished.
```
## Class diagram
![alt text](./etc/callback.png "Callback")
## Applicability
Use the Callback pattern when
* when some arbitrary synchronous or asynchronous action must be performed after execution of some defined activity.
## Real world examples
* [CyclicBarrier](http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept callback that will be triggered every time when barrier is tripped.
* [CyclicBarrier](http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept a callback that will be triggered every time a barrier is tripped.

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@ -8,11 +8,6 @@ package com.iluwatar.callback {
interface Callback {
+ call() {abstract}
}
class LambdasApp {
- LOGGER : Logger {static}
- LambdasApp()
+ main(args : String[]) {static}
}
class SimpleTask {
- LOGGER : Logger {static}
+ SimpleTask()

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>callback</artifactId>
<dependencies>

View File

@ -9,27 +9,32 @@ tags:
---
## Intent
Avoid coupling the sender of a request to its receiver by giving
more than one object a chance to handle the request. Chain the receiving
objects and pass the request along the chain until an object handles it.
Avoid coupling the sender of a request to its receiver by giving more than one object a chance to
handle the request. Chain the receiving objects and pass the request along the chain until an object
handles it.
## Explanation
Real world example
> The Orc King gives loud orders to his army. The closest one to react is the commander, then officer and then soldier. The commander, officer and soldier here form a chain of responsibility.
> The Orc King gives loud orders to his army. The closest one to react is the commander, then
> officer and then soldier. The commander, officer and soldier here form a chain of responsibility.
In plain words
> It helps building a chain of objects. Request enters from one end and keeps going from object to object till it finds the suitable handler.
> It helps to build a chain of objects. A request enters from one end and keeps going from an object
> to another until it finds a suitable handler.
Wikipedia says
> In object-oriented design, the chain-of-responsibility pattern is a design pattern consisting of a source of command objects and a series of processing objects. Each processing object contains logic that defines the types of command objects that it can handle; the rest are passed to the next processing object in the chain.
> In object-oriented design, the chain-of-responsibility pattern is a design pattern consisting of
> a source of command objects and a series of processing objects. Each processing object contains
> logic that defines the types of command objects that it can handle; the rest are passed to the
> next processing object in the chain.
**Programmatic Example**
Translating our example with orcs from above. First we have the request class
Translating our example with the orcs from above. First we have the `Request` class:
```java
public class Request {
@ -140,14 +145,16 @@ king.makeRequest(new Request(RequestType.COLLECT_TAX, "collect tax")); // Orc so
```
## Class diagram
![alt text](./etc/chain.urm.png "Chain of Responsibility class diagram")
## Applicability
Use Chain of Responsibility when
* more than one object may handle a request, and the handler isn't known a priori. The handler should be ascertained automatically
* you want to issue a request to one of several objects without specifying the receiver explicitly
* the set of objects that can handle a request should be specified dynamically
* More than one object may handle a request, and the handler isn't known a priori. The handler should be ascertained automatically.
* You want to issue a request to one of several objects without specifying the receiver explicitly.
* The set of objects that can handle a request should be specified dynamically.
## Real world examples

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>chain</artifactId>
<dependencies>

View File

@ -12,167 +12,304 @@ tags:
## Intent
Handle costly remote *procedure/service* calls in such a way that the failure of a **single** service/component cannot bring the whole application down, and we can reconnect to the service as soon as possible.
Handle costly remote service calls in such a way that the failure of a single service/component
cannot bring the whole application down, and we can reconnect to the service as soon as possible.
## Explanation
Real world example
> Imagine a Web App that has both local (example: files and images) and remote (example: database entries) to serve. The database might not be responding due to a variety of reasons, so if the application keeps trying to read from the database using multiple threads/processes, soon all of them will hang and our entire web application will crash. We should be able to detect this situation and show the user an appropriate message so that he/she can explore other parts of the app unaffected by the database failure without any problem.
> Imagine a web application that has both local files/images and remote services that are used for
> fetching data. These remote services may be either healthy and responsive at times, or may become
> slow and unresponsive at some point of time due to variety of reasons. So if one of the remote
> services is slow or not responding successfully, our application will try to fetch response from
> the remote service using multiple threads/processes, soon all of them will hang (also called
> [thread starvation](https://en.wikipedia.org/wiki/Starvation_(computer_science))) causing our entire web application to crash. We should be able to detect
> this situation and show the user an appropriate message so that he/she can explore other parts of
> the app unaffected by the remote service failure. Meanwhile, the other services that are working
> normally, should keep functioning unaffected by this failure.
In plain words
> Allows us to save resources when we know a remote service failed. Useful when all parts of our application are highly decoupled from each other, and failure of one component doesn't mean the other parts will stop working.
> Circuit Breaker allows graceful handling of failed remote services. It's especially useful when
> all parts of our application are highly decoupled from each other, and failure of one component
> doesn't mean the other parts will stop working.
Wikipedia says
> **Circuit breaker** is a design pattern used in modern software development. It is used to detect failures and encapsulates the logic of preventing a failure from constantly recurring, during maintenance, temporary external system failure or unexpected system difficulties.
So, how does this all come together?
> Circuit breaker is a design pattern used in modern software development. It is used to detect
> failures and encapsulates the logic of preventing a failure from constantly recurring, during
> maintenance, temporary external system failure or unexpected system difficulties.
## Programmatic Example
With the above example in mind we will imitate the functionality in a simple manner. We have two services: A *monitoring service* which will mimic the web app and will make both **local** and **remote** calls.
So, how does this all come together? With the above example in mind we will imitate the
functionality in a simple example. A monitoring service mimics the web app and makes both local and
remote calls.
The service architecture is as follows:
![alt text](./etc/ServiceDiagram.PNG "Service Diagram")
In terms of code, the End user application is:
In terms of code, the end user application is:
```java
public class App {
private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
/**
* Program entry point.
*
* @param args command line args
*/
public static void main(String[] args) {
var obj = new MonitoringService();
var circuitBreaker = new CircuitBreaker(3000, 1, 2000 * 1000 * 1000);
var serverStartTime = System.nanoTime();
while (true) {
LOGGER.info(obj.localResourceResponse());
LOGGER.info(obj.remoteResourceResponse(circuitBreaker, serverStartTime));
LOGGER.info(circuitBreaker.getState());
try {
Thread.sleep(5 * 1000);
} catch (InterruptedException e) {
LOGGER.error(e.getMessage());
}
var delayedService = new DelayedRemoteService(serverStartTime, 5);
var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000, 2,
2000 * 1000 * 1000);
var quickService = new QuickRemoteService();
var quickServiceCircuitBreaker = new DefaultCircuitBreaker(quickService, 3000, 2,
2000 * 1000 * 1000);
//Create an object of monitoring service which makes both local and remote calls
var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,
quickServiceCircuitBreaker);
//Fetch response from local resource
LOGGER.info(monitoringService.localResourceResponse());
//Fetch response from delayed service 2 times, to meet the failure threshold
LOGGER.info(monitoringService.delayedServiceResponse());
LOGGER.info(monitoringService.delayedServiceResponse());
//Fetch current state of delayed service circuit breaker after crossing failure threshold limit
//which is OPEN now
LOGGER.info(delayedServiceCircuitBreaker.getState());
//Meanwhile, the delayed service is down, fetch response from the healthy quick service
LOGGER.info(monitoringService.quickServiceResponse());
LOGGER.info(quickServiceCircuitBreaker.getState());
//Wait for the delayed service to become responsive
try {
LOGGER.info("Waiting for delayed service to become responsive");
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//Check the state of delayed circuit breaker, should be HALF_OPEN
LOGGER.info(delayedServiceCircuitBreaker.getState());
//Fetch response from delayed service, which should be healthy by now
LOGGER.info(monitoringService.delayedServiceResponse());
//As successful response is fetched, it should be CLOSED again.
LOGGER.info(delayedServiceCircuitBreaker.getState());
}
}
```
The monitoring service is:
The monitoring service:
``` java
```java
public class MonitoringService {
private final CircuitBreaker delayedService;
private final CircuitBreaker quickService;
public MonitoringService(CircuitBreaker delayedService, CircuitBreaker quickService) {
this.delayedService = delayedService;
this.quickService = quickService;
}
//Assumption: Local service won't fail, no need to wrap it in a circuit breaker logic
public String localResourceResponse() {
return "Local Service is working";
}
public String remoteResourceResponse(CircuitBreaker circuitBreaker, long serverStartTime) {
/**
* Fetch response from the delayed service (with some simulated startup time).
*
* @return response string
*/
public String delayedServiceResponse() {
try {
return circuitBreaker.call("delayedService", serverStartTime);
} catch (Exception e) {
return this.delayedService.attemptRequest();
} catch (RemoteServiceException e) {
return e.getMessage();
}
}
/**
* Fetches response from a healthy service without any failure.
*
* @return response string
*/
public String quickServiceResponse() {
try {
return this.quickService.attemptRequest();
} catch (RemoteServiceException e) {
return e.getMessage();
}
}
}
```
As it can be seen, it does the call to get local resources directly, but it wraps the call to remote (costly) service in a circuit breaker object, which prevents faults as follows:
As it can be seen, it does the call to get local resources directly, but it wraps the call to
remote (costly) service in a circuit breaker object, which prevents faults as follows:
```java
public class CircuitBreaker {
public class DefaultCircuitBreaker implements CircuitBreaker {
private final long timeout;
private final long retryTimePeriod;
private final RemoteService service;
long lastFailureTime;
private String lastFailureResponse;
int failureCount;
private final int failureThreshold;
private State state;
private final long futureTime = 1000 * 1000 * 1000 * 1000;
CircuitBreaker(long timeout, int failureThreshold, long retryTimePeriod) {
/**
* Constructor to create an instance of Circuit Breaker.
*
* @param timeout Timeout for the API request. Not necessary for this simple example
* @param failureThreshold Number of failures we receive from the depended service before changing
* state to 'OPEN'
* @param retryTimePeriod Time period after which a new request is made to remote service for
* status check.
*/
DefaultCircuitBreaker(RemoteService serviceToCall, long timeout, int failureThreshold,
long retryTimePeriod) {
this.service = serviceToCall;
// We start in a closed state hoping that everything is fine
this.state = State.CLOSED;
this.failureThreshold = failureThreshold;
// Timeout for the API request.
// Used to break the calls made to remote resource if it exceeds the limit
this.timeout = timeout;
this.retryTimePeriod = retryTimePeriod;
//An absurd amount of time in future which basically indicates the last failure never happened
this.lastFailureTime = System.nanoTime() + futureTime;
this.failureCount = 0;
}
private void reset() {
// Reset everything to defaults
@Override
public void recordSuccess() {
this.failureCount = 0;
this.lastFailureTime = System.nanoTime() + futureTime;
this.lastFailureTime = System.nanoTime() + futureTime;
this.state = State.CLOSED;
}
private void recordFailure() {
@Override
public void recordFailure(String response) {
failureCount = failureCount + 1;
this.lastFailureTime = System.nanoTime();
// Cache the failure response for returning on open state
this.lastFailureResponse = response;
}
protected void setState() {
if (failureCount > failureThreshold) {
// Evaluate the current state based on failureThreshold, failureCount and lastFailureTime.
protected void evaluateState() {
if (failureCount >= failureThreshold) { //Then something is wrong with remote service
if ((System.nanoTime() - lastFailureTime) > retryTimePeriod) {
//We have waited long enough and should try checking if service is up
state = State.HALF_OPEN;
} else {
//Service would still probably be down
state = State.OPEN;
}
} else {
//Everything is working fine
state = State.CLOSED;
}
}
@Override
public String getState() {
evaluateState();
return state.name();
}
public void setStateForBypass(State state) {
/**
* Break the circuit beforehand if it is known service is down Or connect the circuit manually if
* service comes online before expected.
*
* @param state State at which circuit is in
*/
@Override
public void setState(State state) {
this.state = state;
switch (state) {
case OPEN:
this.failureCount = failureThreshold;
this.lastFailureTime = System.nanoTime();
break;
case HALF_OPEN:
this.failureCount = failureThreshold;
this.lastFailureTime = System.nanoTime() - retryTimePeriod;
break;
default:
this.failureCount = 0;
}
}
public String call(String serviceToCall, long serverStartTime) throws Exception {
setState();
/**
* Executes service call.
*
* @return Value from the remote resource, stale response or a custom exception
*/
@Override
public String attemptRequest() throws RemoteServiceException {
evaluateState();
if (state == State.OPEN) {
return "This is stale response from API";
// return cached response if the circuit is in OPEN state
return this.lastFailureResponse;
} else {
if (serviceToCall.equals("delayedService")) {
var delayedService = new DelayedService(20);
var response = delayedService.response(serverStartTime);
if (response.split(" ")[3].equals("working")) {
reset();
return response;
} else {
recordFailure();
throw new Exception("Remote service not responding");
}
} else {
throw new Exception("Unknown Service Name");
// Make the API request if the circuit is not OPEN
try {
//In a real application, this would be run in a thread and the timeout
//parameter of the circuit breaker would be utilized to know if service
//is working. Here, we simulate that based on server response itself
var response = service.call();
// Yay!! the API responded fine. Let's reset everything.
recordSuccess();
return response;
} catch (RemoteServiceException ex) {
recordFailure(ex.getMessage());
throw ex;
}
}
}
}
```
How does the above pattern prevent failures? Let's understand via this finite state machine implemented by it.
How does the above pattern prevent failures? Let's understand via this finite state machine
implemented by it.
![alt text](./etc/StateDiagram.PNG "State Diagram")
- We initialize the Circuit Breaker object with certain parameters: **timeout**, **failureThreshold** and **retryTimePeriod** which help determine how resilient the API is.
- Initially, we are in the **closed** state and the remote call to API happens.
- We initialize the Circuit Breaker object with certain parameters: `timeout`, `failureThreshold` and `retryTimePeriod` which help determine how resilient the API is.
- Initially, we are in the `closed` state and nos remote calls to the API have occurred.
- Every time the call succeeds, we reset the state to as it was in the beginning.
- If the number of failures cross a certain threshold, we move to the **open** state, which acts just like an open circuit and prevents remote service calls from being made, thus saving resources. (Here, we return the response called ```stale response from API```)
- Once we exceed the retry timeout period, we move to the **half-open** state and make another call to the remote service again to check if the service is working so that we can serve fresh content. A *failure* sets it back to **open** state and another attempt is made after retry timeout period, while a *success* sets it to **closed** state so that everything starts working normally again.
- If the number of failures cross a certain threshold, we move to the `open` state, which acts just like an open circuit and prevents remote service calls from being made, thus saving resources. (Here, we return the response called ```stale response from API```)
- Once we exceed the retry timeout period, we move to the `half-open` state and make another call to the remote service again to check if the service is working so that we can serve fresh content. A failure sets it back to `open` state and another attempt is made after retry timeout period, while a success sets it to `closed` state so that everything starts working normally again.
## Class diagram
![alt text](./etc/circuit-breaker.urm.png "Circuit Breaker class diagram")
## Applicability
Use the Circuit Breaker pattern when
- Building a fault-tolerant application where failure of some services shouldn't bring the entire application down.
- Building an continuously incremental/continuous delivery application, as some of it's components can be upgraded without shutting it down entirely.
- Building a continuously running (always-on) application, so that its components can be upgraded without shutting it down entirely.
## Related Patterns

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@ -5,32 +5,52 @@ package com.iluwatar.circuitbreaker {
+ App()
+ main(args : String[]) {static}
}
class CircuitBreaker {
interface CircuitBreaker {
+ attemptRequest() : String {abstract}
+ getState() : String {abstract}
+ recordFailure(String) {abstract}
+ recordSuccess() {abstract}
+ setState(State) {abstract}
}
class DefaultCircuitBreaker {
~ failureCount : int
- failureThreshold : int
- futureTime : long
- lastFailureResponse : String
~ lastFailureTime : long
- retryTimePeriod : long
- service : RemoteService
- state : State
- timeout : long
~ CircuitBreaker(timeout : long, failureThreshold : int, retryTimePeriod : long)
+ call(serviceToCall : String, serverStartTime : long) : String
~ DefaultCircuitBreaker(serviceToCall : RemoteService, timeout : long, failureThreshold : int, retryTimePeriod : long)
+ attemptRequest() : String
# evaluateState()
+ getState() : String
- recordFailure()
- reset()
# setState()
+ setStateForBypass(state : State)
+ recordFailure(response : String)
+ recordSuccess()
+ setState(state : State)
}
class DelayedService {
class DelayedRemoteService {
- delay : int
+ DelayedService()
+ DelayedService(delay : int)
+ response(serverStartTime : long) : String
- serverStartTime : long
+ DelayedRemoteService()
+ DelayedRemoteService(serverStartTime : long, delay : int)
+ call() : String
}
class MonitoringService {
+ MonitoringService()
- delayedService : CircuitBreaker
- quickService : CircuitBreaker
+ MonitoringService(delayedService : CircuitBreaker, quickService : CircuitBreaker)
+ delayedServiceResponse() : String
+ localResourceResponse() : String
+ remoteResourceResponse(circuitBreaker : CircuitBreaker, serverStartTime : long) : String
+ quickServiceResponse() : String
}
class QuickRemoteService {
+ QuickRemoteService()
+ call() : String
}
interface RemoteService {
+ call() : String {abstract}
}
enum State {
+ CLOSED {static}
@ -40,5 +60,10 @@ package com.iluwatar.circuitbreaker {
+ values() : State[] {static}
}
}
CircuitBreaker --> "-state" State
DefaultCircuitBreaker --> "-state" State
MonitoringService --> "-delayedService" CircuitBreaker
DefaultCircuitBreaker --> "-service" RemoteService
DefaultCircuitBreaker ..|> CircuitBreaker
DelayedRemoteService ..|> RemoteService
QuickRemoteService ..|> RemoteService
@enduml

View File

@ -27,7 +27,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>circuit-breaker</artifactId>
<dependencies>

View File

@ -36,17 +36,18 @@ import org.slf4j.LoggerFactory;
* operational again, so that we can use it
* </p>
* <p>
* In this example, the circuit breaker pattern is demonstrated by using two services: {@link
* MonitoringService} and {@link DelayedService}. The monitoring service is responsible for calling
* two services: a local service and a remote service {@link DelayedService} , and by using the
* circuit breaker construction we ensure that if the call to remote service is going to fail, we
* are going to save our resources and not make the function call at all, by wrapping our call to
* the remote service in the circuit breaker object.
* In this example, the circuit breaker pattern is demonstrated by using three services: {@link
* DelayedRemoteService}, {@link QuickRemoteService} and {@link MonitoringService}. The monitoring
* service is responsible for calling three services: a local service, a quick remove service
* {@link QuickRemoteService} and a delayed remote service {@link DelayedRemoteService} , and by
* using the circuit breaker construction we ensure that if the call to remote service is going to
* fail, we are going to save our resources and not make the function call at all, by wrapping our
* call to the remote services in the {@link DefaultCircuitBreaker} implementation object.
* </p>
* <p>
* This works as follows: The {@link CircuitBreaker} object can be in one of three states:
* <b>Open</b>, <b>Closed</b> and <b>Half-Open</b>, which represents the real world circuits. If the
* state is closed (initial), we assume everything is alright and perform the function call.
* This works as follows: The {@link DefaultCircuitBreaker} object can be in one of three states:
* <b>Open</b>, <b>Closed</b> and <b>Half-Open</b>, which represents the real world circuits. If
* the state is closed (initial), we assume everything is alright and perform the function call.
* However, every time the call fails, we note it and once it crosses a threshold, we set the state
* to Open, preventing any further calls to the remote server. Then, after a certain retry period
* (during which we expect thee service to recover), we make another call to the remote server and
@ -63,22 +64,50 @@ public class App {
*
* @param args command line args
*/
@SuppressWarnings("squid:S2189")
public static void main(String[] args) {
//Create an object of monitoring service which makes both local and remote calls
var obj = new MonitoringService();
//Set the circuit Breaker parameters
var circuitBreaker = new CircuitBreaker(3000, 1, 2000 * 1000 * 1000);
var serverStartTime = System.nanoTime();
while (true) {
LOGGER.info(obj.localResourceResponse());
LOGGER.info(obj.remoteResourceResponse(circuitBreaker, serverStartTime));
LOGGER.info(circuitBreaker.getState());
try {
Thread.sleep(5 * 1000);
} catch (InterruptedException e) {
LOGGER.error(e.getMessage());
}
var delayedService = new DelayedRemoteService(serverStartTime, 5);
var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000, 2,
2000 * 1000 * 1000);
var quickService = new QuickRemoteService();
var quickServiceCircuitBreaker = new DefaultCircuitBreaker(quickService, 3000, 2,
2000 * 1000 * 1000);
//Create an object of monitoring service which makes both local and remote calls
var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,
quickServiceCircuitBreaker);
//Fetch response from local resource
LOGGER.info(monitoringService.localResourceResponse());
//Fetch response from delayed service 2 times, to meet the failure threshold
LOGGER.info(monitoringService.delayedServiceResponse());
LOGGER.info(monitoringService.delayedServiceResponse());
//Fetch current state of delayed service circuit breaker after crossing failure threshold limit
//which is OPEN now
LOGGER.info(delayedServiceCircuitBreaker.getState());
//Meanwhile, the delayed service is down, fetch response from the healthy quick service
LOGGER.info(monitoringService.quickServiceResponse());
LOGGER.info(quickServiceCircuitBreaker.getState());
//Wait for the delayed service to become responsive
try {
LOGGER.info("Waiting for delayed service to become responsive");
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//Check the state of delayed circuit breaker, should be HALF_OPEN
LOGGER.info(delayedServiceCircuitBreaker.getState());
//Fetch response from delayed service, which should be healthy by now
LOGGER.info(monitoringService.delayedServiceResponse());
//As successful response is fetched, it should be CLOSED again.
LOGGER.info(delayedServiceCircuitBreaker.getState());
}
}

View File

@ -24,114 +24,22 @@
package com.iluwatar.circuitbreaker;
/**
* The circuit breaker class with all configurations.
* The Circuit breaker interface.
*/
public class CircuitBreaker {
private final long timeout;
private final long retryTimePeriod;
long lastFailureTime;
int failureCount;
private final int failureThreshold;
private State state;
private final long futureTime = 1000 * 1000 * 1000 * 1000;
public interface CircuitBreaker {
/**
* Constructor to create an instance of Circuit Breaker.
*
* @param timeout Timeout for the API request. Not necessary for this simple example
* @param failureThreshold Number of failures we receive from the depended service before changing
* state to 'OPEN'
* @param retryTimePeriod Time period after which a new request is made to remote service for
* status check.
*/
CircuitBreaker(long timeout, int failureThreshold, long retryTimePeriod) {
// We start in a closed state hoping that everything is fine
this.state = State.CLOSED;
this.failureThreshold = failureThreshold;
// Timeout for the API request.
// Used to break the calls made to remote resource if it exceeds the limit
this.timeout = timeout;
this.retryTimePeriod = retryTimePeriod;
//An absurd amount of time in future which basically indicates the last failure never happened
this.lastFailureTime = System.nanoTime() + futureTime;
this.failureCount = 0;
}
// Success response. Reset everything to defaults
void recordSuccess();
//Reset everything to defaults
private void reset() {
this.failureCount = 0;
this.lastFailureTime = System.nanoTime() + futureTime;
this.state = State.CLOSED;
}
// Failure response. Handle accordingly with response and change state if required.
void recordFailure(String response);
private void recordFailure() {
failureCount = failureCount + 1;
this.lastFailureTime = System.nanoTime();
}
// Get the current state of circuit breaker
String getState();
protected void setState() {
if (failureCount > failureThreshold) { //Then something is wrong with remote service
if ((System.nanoTime() - lastFailureTime) > retryTimePeriod) {
//We have waited long enough and should try checking if service is up
state = State.HALF_OPEN;
} else {
//Service would still probably be down
state = State.OPEN;
}
} else {
//Everything is working fine
state = State.CLOSED;
}
}
// Set the specific state manually.
void setState(State state);
public String getState() {
return state.name();
}
/**
* Break the circuit beforehand if it is known service is down Or connect the circuit manually if
* service comes online before expected.
*
* @param state State at which circuit is in
*/
public void setStateForBypass(State state) {
this.state = state;
}
/**
* Executes service call.
*
* @param serviceToCall The name of the service in String. Can be changed to data URLs in case
* of web applications
* @param serverStartTime Time at which actual server was started which makes calls to this
* service
* @return Value from the remote resource, stale response or a custom exception
*/
public String call(String serviceToCall, long serverStartTime) throws Exception {
setState();
if (state == State.OPEN) {
// return cached response if no the circuit is in OPEN state
return "This is stale response from API";
} else {
// Make the API request if the circuit is not OPEN
if (serviceToCall.equals("delayedService")) {
var delayedService = new DelayedService(20);
var response = delayedService.response(serverStartTime);
//In a real application, this would be run in a thread and the timeout
//parameter of the circuit breaker would be utilized to know if service
//is working. Here, we simulate that based on server response itself
if (response.split(" ")[3].equals("working")) {
// Yay!! the API responded fine. Let's reset everything.
reset();
return response;
} else {
// Uh-oh!! the call still failed. Let's update that in our records.
recordFailure();
throw new Exception("Remote service not responding");
}
} else {
throw new Exception("Unknown Service Name");
}
}
}
}
// Attempt to fetch response from the remote service.
String attemptRequest() throws RemoteServiceException;
}

View File

@ -0,0 +1,155 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.circuitbreaker;
/**
* The delay based Circuit breaker implementation that works in a
* CLOSED->OPEN-(retry_time_period)->HALF_OPEN->CLOSED flow with some retry time period for failed
* services and a failure threshold for service to open circuit.
*/
public class DefaultCircuitBreaker implements CircuitBreaker {
private final long timeout;
private final long retryTimePeriod;
private final RemoteService service;
long lastFailureTime;
private String lastFailureResponse;
int failureCount;
private final int failureThreshold;
private State state;
private final long futureTime = 1000 * 1000 * 1000 * 1000;
/**
* Constructor to create an instance of Circuit Breaker.
*
* @param timeout Timeout for the API request. Not necessary for this simple example
* @param failureThreshold Number of failures we receive from the depended service before changing
* state to 'OPEN'
* @param retryTimePeriod Time period after which a new request is made to remote service for
* status check.
*/
DefaultCircuitBreaker(RemoteService serviceToCall, long timeout, int failureThreshold,
long retryTimePeriod) {
this.service = serviceToCall;
// We start in a closed state hoping that everything is fine
this.state = State.CLOSED;
this.failureThreshold = failureThreshold;
// Timeout for the API request.
// Used to break the calls made to remote resource if it exceeds the limit
this.timeout = timeout;
this.retryTimePeriod = retryTimePeriod;
//An absurd amount of time in future which basically indicates the last failure never happened
this.lastFailureTime = System.nanoTime() + futureTime;
this.failureCount = 0;
}
// Reset everything to defaults
@Override
public void recordSuccess() {
this.failureCount = 0;
this.lastFailureTime = System.nanoTime() + futureTime;
this.state = State.CLOSED;
}
@Override
public void recordFailure(String response) {
failureCount = failureCount + 1;
this.lastFailureTime = System.nanoTime();
// Cache the failure response for returning on open state
this.lastFailureResponse = response;
}
// Evaluate the current state based on failureThreshold, failureCount and lastFailureTime.
protected void evaluateState() {
if (failureCount >= failureThreshold) { //Then something is wrong with remote service
if ((System.nanoTime() - lastFailureTime) > retryTimePeriod) {
//We have waited long enough and should try checking if service is up
state = State.HALF_OPEN;
} else {
//Service would still probably be down
state = State.OPEN;
}
} else {
//Everything is working fine
state = State.CLOSED;
}
}
@Override
public String getState() {
evaluateState();
return state.name();
}
/**
* Break the circuit beforehand if it is known service is down Or connect the circuit manually if
* service comes online before expected.
*
* @param state State at which circuit is in
*/
@Override
public void setState(State state) {
this.state = state;
switch (state) {
case OPEN:
this.failureCount = failureThreshold;
this.lastFailureTime = System.nanoTime();
break;
case HALF_OPEN:
this.failureCount = failureThreshold;
this.lastFailureTime = System.nanoTime() - retryTimePeriod;
break;
default:
this.failureCount = 0;
}
}
/**
* Executes service call.
*
* @return Value from the remote resource, stale response or a custom exception
*/
@Override
public String attemptRequest() throws RemoteServiceException {
evaluateState();
if (state == State.OPEN) {
// return cached response if the circuit is in OPEN state
return this.lastFailureResponse;
} else {
// Make the API request if the circuit is not OPEN
try {
//In a real application, this would be run in a thread and the timeout
//parameter of the circuit breaker would be utilized to know if service
//is working. Here, we simulate that based on server response itself
var response = service.call();
// Yay!! the API responded fine. Let's reset everything.
recordSuccess();
return response;
} catch (RemoteServiceException ex) {
recordFailure(ex.getMessage());
throw ex;
}
}
}
}

View File

@ -27,7 +27,9 @@ package com.iluwatar.circuitbreaker;
* This simulates the remote service It responds only after a certain timeout period (default set to
* 20 seconds).
*/
public class DelayedService {
public class DelayedRemoteService implements RemoteService {
private final long serverStartTime;
private final int delay;
/**
@ -35,22 +37,23 @@ public class DelayedService {
*
* @param delay the delay after which service would behave properly, in seconds
*/
public DelayedService(int delay) {
public DelayedRemoteService(long serverStartTime, int delay) {
this.serverStartTime = serverStartTime;
this.delay = delay;
}
public DelayedService() {
this.delay = 60;
public DelayedRemoteService() {
this.serverStartTime = System.nanoTime();
this.delay = 20;
}
/**
* Responds based on delay, current time and server start time if the service is down / working.
*
* @param serverStartTime Time at which actual server was started which makes calls to this
* service
* @return The state of the service
*/
public String response(long serverStartTime) {
@Override
public String call() throws RemoteServiceException {
var currentTime = System.nanoTime();
//Since currentTime and serverStartTime are both in nanoseconds, we convert it to
//seconds by diving by 10e9 and ensure floating point division by multiplying it
@ -58,9 +61,8 @@ public class DelayedService {
//send the reply
if ((currentTime - serverStartTime) * 1.0 / (1000 * 1000 * 1000) < delay) {
//Can use Thread.sleep() here to block and simulate a hung server
return "Delayed service is down";
} else {
return "Delayed service is working";
throw new RemoteServiceException("Delayed service is down");
}
return "Delayed service is working";
}
}

View File

@ -24,28 +24,47 @@
package com.iluwatar.circuitbreaker;
/**
* The service class which makes local and remote calls Uses {@link CircuitBreaker} object to ensure
* remote calls don't use up resources.
* The service class which makes local and remote calls Uses {@link DefaultCircuitBreaker} object to
* ensure remote calls don't use up resources.
*/
public class MonitoringService {
private final CircuitBreaker delayedService;
private final CircuitBreaker quickService;
public MonitoringService(CircuitBreaker delayedService, CircuitBreaker quickService) {
this.delayedService = delayedService;
this.quickService = quickService;
}
//Assumption: Local service won't fail, no need to wrap it in a circuit breaker logic
public String localResourceResponse() {
return "Local Service is working";
}
/**
* Try to get result from remote server.
* Fetch response from the delayed service (with some simulated startup time).
*
* @param circuitBreaker The circuitBreaker object with all parameters
* @param serverStartTime Time at which actual server was started which makes calls to this
* service
* @return result from the remote response or exception raised by it.
* @return response string
*/
public String remoteResourceResponse(CircuitBreaker circuitBreaker, long serverStartTime) {
public String delayedServiceResponse() {
try {
return circuitBreaker.call("delayedService", serverStartTime);
} catch (Exception e) {
return this.delayedService.attemptRequest();
} catch (RemoteServiceException e) {
return e.getMessage();
}
}
/**
* Fetches response from a healthy service without any failure.
*
* @return response string
*/
public String quickServiceResponse() {
try {
return this.quickService.attemptRequest();
} catch (RemoteServiceException e) {
return e.getMessage();
}
}

View File

@ -0,0 +1,35 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.circuitbreaker;
/**
* A quick response remote service, that responds healthy without any delay or failure.
*/
public class QuickRemoteService implements RemoteService {
@Override
public String call() throws RemoteServiceException {
return "Quick Service is working";
}
}

View File

@ -0,0 +1,34 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.circuitbreaker;
/**
* The Remote service interface, used by {@link CircuitBreaker} for fetching response from remote
* services.
*/
public interface RemoteService {
//Fetch response from remote service.
String call() throws RemoteServiceException;
}

View File

@ -0,0 +1,34 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.circuitbreaker;
/**
* Exception thrown when {@link RemoteService} does not respond successfully.
*/
public class RemoteServiceException extends Exception {
public RemoteServiceException(String message) {
super(message);
}
}

View File

@ -0,0 +1,135 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.circuitbreaker;
import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* App Test showing usage of circuit breaker.
*/
public class AppTest {
private static final Logger LOGGER = LoggerFactory.getLogger(AppTest.class);
//Startup delay for delayed service (in seconds)
private static final int STARTUP_DELAY = 4;
//Number of failed requests for circuit breaker to open
private static final int FAILURE_THRESHOLD = 1;
//Time period in seconds for circuit breaker to retry service
private static final int RETRY_PERIOD = 2;
private MonitoringService monitoringService;
private CircuitBreaker delayedServiceCircuitBreaker;
private CircuitBreaker quickServiceCircuitBreaker;
/**
* Setup the circuit breakers and services, where {@link DelayedRemoteService} will be start with
* a delay of 4 seconds and a {@link QuickRemoteService} responding healthy. Both services are
* wrapped in a {@link DefaultCircuitBreaker} implementation with failure threshold of 1 failure
* and retry time period of 2 seconds.
*/
@BeforeEach
public void setupCircuitBreakers() {
var delayedService = new DelayedRemoteService(System.nanoTime(), STARTUP_DELAY);
//Set the circuit Breaker parameters
delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
FAILURE_THRESHOLD,
RETRY_PERIOD * 1000 * 1000 * 1000);
var quickService = new QuickRemoteService();
//Set the circuit Breaker parameters
quickServiceCircuitBreaker = new DefaultCircuitBreaker(quickService, 3000, FAILURE_THRESHOLD,
RETRY_PERIOD * 1000 * 1000 * 1000);
monitoringService = new MonitoringService(delayedServiceCircuitBreaker,
quickServiceCircuitBreaker);
}
@Test
public void testFailure_OpenStateTransition() {
//Calling delayed service, which will be unhealthy till 4 seconds
assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
//As failure threshold is "1", the circuit breaker is changed to OPEN
assertEquals("OPEN", delayedServiceCircuitBreaker.getState());
//As circuit state is OPEN, we expect a quick fallback response from circuit breaker.
assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
//Meanwhile, the quick service is responding and the circuit state is CLOSED
assertEquals("Quick Service is working", monitoringService.quickServiceResponse());
assertEquals("CLOSED", quickServiceCircuitBreaker.getState());
}
@Test
public void testFailure_HalfOpenStateTransition() {
//Calling delayed service, which will be unhealthy till 4 seconds
assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
//As failure threshold is "1", the circuit breaker is changed to OPEN
assertEquals("OPEN", delayedServiceCircuitBreaker.getState());
//Waiting for recovery period of 2 seconds for circuit breaker to retry service.
try {
LOGGER.info("Waiting 2s for delayed service to become responsive");
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//After 2 seconds, the circuit breaker should move to "HALF_OPEN" state and retry fetching response from service again
assertEquals("HALF_OPEN", delayedServiceCircuitBreaker.getState());
}
@Test
public void testRecovery_ClosedStateTransition() {
//Calling delayed service, which will be unhealthy till 4 seconds
assertEquals("Delayed service is down", monitoringService.delayedServiceResponse());
//As failure threshold is "1", the circuit breaker is changed to OPEN
assertEquals("OPEN", delayedServiceCircuitBreaker.getState());
//Waiting for 4 seconds, which is enough for DelayedService to become healthy and respond successfully.
try {
LOGGER.info("Waiting 4s for delayed service to become responsive");
Thread.sleep(4000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//As retry period is 2 seconds (<4 seconds of wait), hence the circuit breaker should be back in HALF_OPEN state.
assertEquals("HALF_OPEN", delayedServiceCircuitBreaker.getState());
//Check the success response from delayed service.
assertEquals("Delayed service is working", monitoringService.delayedServiceResponse());
//As the response is success, the state should be CLOSED
assertEquals("CLOSED", delayedServiceCircuitBreaker.getState());
}
}

View File

@ -25,56 +25,60 @@ package com.iluwatar.circuitbreaker;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.rmi.Remote;
import org.junit.jupiter.api.Test;
/**
* Circuit Breaker test
*/
public class CircuitBreakerTest {
public class DefaultCircuitBreakerTest {
//long timeout, int failureThreshold, long retryTimePeriod
@Test
public void testSetState() {
var circuitBreaker = new CircuitBreaker(1, 1, 100);
public void testEvaluateState() {
var circuitBreaker = new DefaultCircuitBreaker(null, 1, 1, 100);
//Right now, failureCount<failureThreshold, so state should be closed
assertEquals(circuitBreaker.getState(), "CLOSED");
circuitBreaker.failureCount = 4;
circuitBreaker.lastFailureTime = System.nanoTime();
circuitBreaker.setState();
circuitBreaker.evaluateState();
//Since failureCount>failureThreshold, and lastFailureTime is nearly equal to current time,
//state should be half-open
assertEquals(circuitBreaker.getState(), "HALF_OPEN");
//Since failureCount>failureThreshold, and lastFailureTime is much lesser current time,
//state should be open
circuitBreaker.lastFailureTime = System.nanoTime() - 1000 * 1000 * 1000 * 1000;
circuitBreaker.setState();
circuitBreaker.evaluateState();
assertEquals(circuitBreaker.getState(), "OPEN");
//Now set it back again to closed to test idempotency
circuitBreaker.failureCount = 0;
circuitBreaker.setState();
circuitBreaker.evaluateState();
assertEquals(circuitBreaker.getState(), "CLOSED");
}
@Test
public void testSetStateForBypass() {
var circuitBreaker = new CircuitBreaker(1, 1, 100);
var circuitBreaker = new DefaultCircuitBreaker(null, 1, 1, 2000 * 1000 * 1000);
//Right now, failureCount<failureThreshold, so state should be closed
//Bypass it and set it to open
circuitBreaker.setStateForBypass(State.OPEN);
circuitBreaker.setState(State.OPEN);
assertEquals(circuitBreaker.getState(), "OPEN");
}
@Test
public void testApiResponses() {
var circuitBreaker = new CircuitBreaker(1, 1, 100);
try {
//Call with the paramater start_time set to huge amount of time in past so that service
//replies with "Ok". Also, state is CLOSED in start
var serviceStartTime = System.nanoTime() - 60 * 1000 * 1000 * 1000;
var response = circuitBreaker.call("delayedService", serviceStartTime);
assertEquals(response, "Delayed service is working");
} catch (Exception e) {
System.out.println(e.getMessage());
}
public void testApiResponses() throws RemoteServiceException {
RemoteService mockService = new RemoteService() {
@Override
public String call() throws RemoteServiceException {
return "Remote Success";
}
};
var circuitBreaker = new DefaultCircuitBreaker(mockService, 1, 1, 100);
//Call with the paramater start_time set to huge amount of time in past so that service
//replies with "Ok". Also, state is CLOSED in start
var serviceStartTime = System.nanoTime() - 60 * 1000 * 1000 * 1000;
var response = circuitBreaker.attemptRequest();
assertEquals(response, "Remote Success");
}
}

View File

@ -0,0 +1,59 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.circuitbreaker;
import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
/**
* Monitoring Service test
*/
public class DelayedRemoteServiceTest {
/**
* Testing immediate response of the delayed service.
*
* @throws RemoteServiceException
*/
@Test
public void testDefaultConstructor() throws RemoteServiceException {
Assertions.assertThrows(RemoteServiceException.class, () -> {
var obj = new DelayedRemoteService();
obj.call();
});
}
/**
* Testing server started in past (2 seconds ago) and with a simulated delay of 1 second.
*
* @throws RemoteServiceException
*/
@Test
public void testParameterizedConstructor() throws RemoteServiceException {
var obj = new DelayedRemoteService(System.nanoTime()-2000*1000*1000,1);
assertEquals("Delayed service is working",obj.call());
}
}

View File

@ -35,28 +35,45 @@ public class MonitoringServiceTest {
//long timeout, int failureThreshold, long retryTimePeriod
@Test
public void testLocalResponse() {
var monitoringService = new MonitoringService();
var monitoringService = new MonitoringService(null,null);
var response = monitoringService.localResourceResponse();
assertEquals(response, "Local Service is working");
}
@Test
public void testRemoteResponse() {
var monitoringService = new MonitoringService();
var circuitBreaker = new CircuitBreaker(1, 1, 100);
public void testDelayedRemoteResponseSuccess() {
var delayedService = new DelayedRemoteService(System.nanoTime()-2*1000*1000*1000, 2);
var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
1,
2 * 1000 * 1000 * 1000);
var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,null);
//Set time in past to make the server work
var serverStartTime = System.nanoTime() / 10;
var response = monitoringService.remoteResourceResponse(circuitBreaker, serverStartTime);
var response = monitoringService.delayedServiceResponse();
assertEquals(response, "Delayed service is working");
}
@Test
public void testRemoteResponse2() {
var monitoringService = new MonitoringService();
var circuitBreaker = new CircuitBreaker(1, 1, 100);
public void testDelayedRemoteResponseFailure() {
var delayedService = new DelayedRemoteService(System.nanoTime(), 2);
var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
1,
2 * 1000 * 1000 * 1000);
var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,null);
//Set time as current time as initially server fails
var serverStartTime = System.nanoTime();
var response = monitoringService.remoteResourceResponse(circuitBreaker, serverStartTime);
assertEquals(response, "Remote service not responding");
var response = monitoringService.delayedServiceResponse();
assertEquals(response, "Delayed service is down");
}
@Test
public void testQuickRemoteServiceResponse() {
var delayedService = new QuickRemoteService();
var delayedServiceCircuitBreaker = new DefaultCircuitBreaker(delayedService, 3000,
1,
2 * 1000 * 1000 * 1000);
var monitoringService = new MonitoringService(delayedServiceCircuitBreaker,null);
//Set time as current time as initially server fails
var response = monitoringService.delayedServiceResponse();
assertEquals(response, "Quick Service is working");
}
}

View File

@ -27,7 +27,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>collection-pipeline</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>combinator</artifactId>

View File

@ -9,15 +9,20 @@ tags:
---
## Also known as
Action, Transaction
## Intent
Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
Encapsulate a request as an object, thereby letting you parameterize clients with different
requests, queue or log requests, and support undoable operations.
## Explanation
Real world example
> There is a wizard casting spells on a goblin. The spells are executed on the goblin one by one. The first spell shrinks the goblin and the second makes him invisible. Then the wizard reverses the spells one by one. Each spell here is a command object that can be undone.
> There is a wizard casting spells on a goblin. The spells are executed on the goblin one by one.
> The first spell shrinks the goblin and the second makes him invisible. Then the wizard reverses
> the spells one by one. Each spell here is a command object that can be undone.
In plain words
@ -25,34 +30,32 @@ In plain words
Wikipedia says
> In object-oriented programming, the command pattern is a behavioral design pattern in which an object is used to encapsulate all information needed to perform an action or trigger an event at a later time.
> In object-oriented programming, the command pattern is a behavioral design pattern in which an
> object is used to encapsulate all information needed to perform an action or trigger an event at
> a later time.
**Programmatic Example**
Here's the sample code with wizard and goblin. Let's start from the wizard class.
Here's the sample code with wizard and goblin. Let's start from the `Wizard` class.
```java
public class Wizard {
private static final Logger LOGGER = LoggerFactory.getLogger(Wizard.class);
private final Deque<Command> undoStack = new LinkedList<>();
private final Deque<Command> redoStack = new LinkedList<>();
public Wizard() {}
public void castSpell(Command command, Target target) {
LOGGER.info("{} casts {} at {}", this, command, target);
command.execute(target);
undoStack.offerLast(command);
public void castSpell(Runnable runnable) {
runnable.run();
undoStack.offerLast(runnable);
}
public void undoLastSpell() {
if (!undoStack.isEmpty()) {
var previousSpell = undoStack.pollLast();
redoStack.offerLast(previousSpell);
LOGGER.info("{} undoes {}", this, previousSpell);
previousSpell.undo();
previousSpell.run();
}
}
@ -60,8 +63,7 @@ public class Wizard {
if (!redoStack.isEmpty()) {
var previousSpell = redoStack.pollLast();
undoStack.offerLast(previousSpell);
LOGGER.info("{} redoes {}", this, previousSpell);
previousSpell.redo();
previousSpell.run();
}
}
@ -72,84 +74,7 @@ public class Wizard {
}
```
Next we present the spell hierarchy.
```java
public interface Command {
void execute(Target target);
void undo();
void redo();
String toString();
}
public class InvisibilitySpell implements Command {
private Target target;
@Override
public void execute(Target target) {
target.setVisibility(Visibility.INVISIBLE);
this.target = target;
}
@Override
public void undo() {
if (target != null) {
target.setVisibility(Visibility.VISIBLE);
}
}
@Override
public void redo() {
if (target != null) {
target.setVisibility(Visibility.INVISIBLE);
}
}
@Override
public String toString() {
return "Invisibility spell";
}
}
public class ShrinkSpell implements Command {
private Size oldSize;
private Target target;
@Override
public void execute(Target target) {
oldSize = target.getSize();
target.setSize(Size.SMALL);
this.target = target;
}
@Override
public void undo() {
if (oldSize != null && target != null) {
var temp = target.getSize();
target.setSize(oldSize);
oldSize = temp;
}
}
@Override
public void redo() {
undo();
}
@Override
public String toString() {
return "Shrink spell";
}
}
```
And last we have the goblin who's the target of the spells.
Next, we have the goblin who's the target of the spells.
```java
public abstract class Target {
@ -196,47 +121,110 @@ public class Goblin extends Target {
return "Goblin";
}
public void changeSize() {
var oldSize = getSize() == Size.NORMAL ? Size.SMALL : Size.NORMAL;
setSize(oldSize);
}
public void changeVisibility() {
var visible = getVisibility() == Visibility.INVISIBLE
? Visibility.VISIBLE : Visibility.INVISIBLE;
setVisibility(visible);
}
}
```
Finally here's the whole example in action.
Finally we have the wizard in main function who casts spell
```java
public static void main(String[] args) {
var wizard = new Wizard();
var goblin = new Goblin();
// casts shrink/unshrink spell
wizard.castSpell(goblin::changeSize);
// casts visible/invisible spell
wizard.castSpell(goblin::changeVisibility);
// undo and redo casts
wizard.undoLastSpell();
wizard.redoLastSpell();
```
Here's the whole example in action.
```java
var wizard = new Wizard();
var goblin = new Goblin();
goblin.printStatus();
// Goblin, [size=normal] [visibility=visible]
wizard.castSpell(new ShrinkSpell(), goblin);
// Wizard casts Shrink spell at Goblin
wizard.castSpell(goblin::changeSize);
goblin.printStatus();
// Goblin, [size=small] [visibility=visible]
wizard.castSpell(new InvisibilitySpell(), goblin);
// Wizard casts Invisibility spell at Goblin
wizard.castSpell(goblin::changeVisibility);
goblin.printStatus();
// Goblin, [size=small] [visibility=invisible]
wizard.undoLastSpell();
// Wizard undoes Invisibility spell
goblin.printStatus();
// Goblin, [size=small] [visibility=visible]
wizard.undoLastSpell();
goblin.printStatus();
wizard.redoLastSpell();
goblin.printStatus();
wizard.redoLastSpell();
goblin.printStatus();
```
Here's the program output:
```java
Goblin, [size=normal] [visibility=visible]
Goblin, [size=small] [visibility=visible]
Goblin, [size=small] [visibility=invisible]
Goblin, [size=small] [visibility=visible]
Goblin, [size=normal] [visibility=visible]
Goblin, [size=small] [visibility=visible]
Goblin, [size=small] [visibility=invisible]
```
## Class diagram
![alt text](./etc/command.png "Command")
## Applicability
Use the Command pattern when you want to
* parameterize objects by an action to perform. You can express such parameterization in a procedural language with a callback function, that is, a function that's registered somewhere to be called at a later point. Commands are an object-oriented replacement for callbacks.
* specify, queue, and execute requests at different times. A Command object can have a lifetime independent of the original request. If the receiver of a request can be represented in an address space-independent way, then you can transfer a command object for the request to a different process and fulfill the request there
* support undo. The Command's execute operation can store state for reversing its effects in the command itself. The Command interface must have an added Unexecute operation that reverses the effects of a previous call to execute. Executed commands are stored in a history list. Unlimited-level undo and redo is achieved by traversing this list backwards and forwards calling unexecute and execute, respectively
* support logging changes so that they can be reapplied in case of a system crash. By augmenting the Command interface with load and store operations, you can keep a persistent log of changes. Recovering from a crash involves reloading logged commands from disk and re-executing them with the execute operation
* structure a system around high-level operations build on primitive operations. Such a structure is common in information systems that support transactions. A transaction encapsulates a set of changes to data. The Command pattern offers a way to model transactions. Commands have a common interface, letting you invoke all transactions the same way. The pattern also makes it easy to extend the system with new transactions
Use the Command pattern when you want to:
* Parameterize objects by an action to perform. You can express such parameterization in a
procedural language with a callback function, that is, a function that's registered somewhere to be
called at a later point. Commands are an object-oriented replacement for callbacks.
* Specify, queue, and execute requests at different times. A Command object can have a lifetime
independent of the original request. If the receiver of a request can be represented in an address
space-independent way, then you can transfer a command object for the request to a different process
and fulfill the request there.
* Support undo. The Command's execute operation can store state for reversing its effects in the
command itself. The Command interface must have an added un-execute operation that reverses the
effects of a previous call to execute. The executed commands are stored in a history list.
Unlimited-level undo and redo is achieved by traversing this list backwards and forwards calling
un-execute and execute, respectively.
* Support logging changes so that they can be reapplied in case of a system crash. By augmenting the
Command interface with load and store operations, you can keep a persistent log of changes.
Recovering from a crash involves reloading logged commands from disk and re-executing them with
the execute operation.
* Structure a system around high-level operations build on primitive operations. Such a structure is
common in information systems that support transactions. A transaction encapsulates a set of changes
to data. The Command pattern offers a way to model transactions. Commands have a common interface,
letting you invoke all transactions the same way. The pattern also makes it easy to extend the
system with new transactions.
## Typical Use Case
* to keep a history of requests
* implement callback functionality
* implement the undo functionality
* To keep a history of requests
* Implement callback functionality
* Implement the undo functionality
## Real world examples

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@ -1,116 +1,89 @@
<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true">
<class id="1" language="java" name="com.iluwatar.command.ShrinkSpell" project="command"
file="/command/src/main/java/com/iluwatar/command/ShrinkSpell.java" binary="false" corner="BOTTOM_RIGHT">
<position height="178" width="141" x="-30" y="681"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="2" language="java" name="com.iluwatar.command.Goblin" project="command"
file="/command/src/main/java/com/iluwatar/command/Goblin.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="129" y="1223"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="3" language="java" name="com.iluwatar.command.Wizard" project="command"
file="/command/src/main/java/com/iluwatar/command/Wizard.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="129" y="362"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="4" language="java" name="com.iluwatar.command.Command" project="command"
file="/command/src/main/java/com/iluwatar/command/Command.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="129" y="561"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="5" language="java" name="com.iluwatar.command.InvisibilitySpell" project="command"
file="/command/src/main/java/com/iluwatar/command/InvisibilitySpell.java" binary="false" corner="BOTTOM_RIGHT">
<position height="160" width="141" x="151" y="681"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="6" language="java" name="com.iluwatar.command.Target" project="command"
file="/command/src/main/java/com/iluwatar/command/Target.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="129" y="1014"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<association id="7">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="8" name="redoStack">
<position height="20" width="67" x="140" y="451"/>
</attribute>
<multiplicity id="9" minimum="0" maximum="2147483647">
<position height="18" width="25" x="221" y="452"/>
</multiplicity>
</end>
<end type="TARGET" refId="4" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<generalization id="10">
<end type="SOURCE" refId="2"/>
<end type="TARGET" refId="6"/>
</generalization>
<association id="11">
<end type="SOURCE" refId="1" navigable="false">
<attribute id="12" name="target"/>
<multiplicity id="13" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="6" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<generalization id="14">
<end type="SOURCE" refId="1"/>
<end type="TARGET" refId="4"/>
</generalization>
<association id="15">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="16" name="undoStack">
<position height="20" width="70" x="-17" y="451"/>
</attribute>
<multiplicity id="17" minimum="0" maximum="2147483647">
<position height="18" width="25" x="60" y="452"/>
</multiplicity>
</end>
<end type="TARGET" refId="4" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<generalization id="18">
<end type="SOURCE" refId="5"/>
<end type="TARGET" refId="4"/>
</generalization>
<association id="19">
<end type="SOURCE" refId="5" navigable="false">
<attribute id="20" name="target"/>
<multiplicity id="21" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="6" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true">
<class id="2" language="java" name="com.iluwatar.command.Goblin" project="command"
file="/command/src/main/java/com/iluwatar/command/Goblin.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="129" y="1223"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="3" language="java" name="com.iluwatar.command.Wizard" project="command"
file="/command/src/main/java/com/iluwatar/command/Wizard.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="129" y="362"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="6" language="java" name="com.iluwatar.command.Target" project="command"
file="/command/src/main/java/com/iluwatar/command/Target.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="129" y="1014"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<association id="7">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="8" name="redoStack">
<position height="20" width="67" x="140" y="451"/>
</attribute>
<multiplicity id="9" minimum="0" maximum="2147483647">
<position height="18" width="25" x="221" y="452"/>
</multiplicity>
</end>
<end type="TARGET" refId="4" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<generalization id="10">
<end type="SOURCE" refId="2"/>
<end type="TARGET" refId="6"/>
</generalization>
<association id="11">
<end type="SOURCE" refId="1" navigable="false">
<attribute id="12" name="target"/>
<multiplicity id="13" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="6" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<generalization id="14">
<end type="SOURCE" refId="1"/>
<end type="TARGET" refId="4"/>
</generalization>
<association id="15">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="16" name="undoStack">
<position height="20" width="70" x="-17" y="451"/>
</attribute>
<multiplicity id="17" minimum="0" maximum="2147483647">
<position height="18" width="25" x="60" y="452"/>
</multiplicity>
</end>
<end type="TARGET" refId="4" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<generalization id="18">
<end type="SOURCE" refId="5"/>
<end type="TARGET" refId="4"/>
</generalization>
<association id="19">
<end type="SOURCE" refId="5" navigable="false">
<attribute id="20" name="target"/>
<multiplicity id="21" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="6" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<association-display labels="true" multiplicity="true"/>
</class-diagram>
</class-diagram>

View File

@ -4,33 +4,11 @@ package com.iluwatar.command {
+ App()
+ main(args : String[]) {static}
}
interface Command {
+ Command()
+ execute(Target) {abstract}
+ redo() {abstract}
+ toString() : String {abstract}
+ undo() {abstract}
}
class Goblin {
+ Goblin()
+ toString() : String
}
class InvisibilitySpell {
- target : Target
+ InvisibilitySpell()
+ execute(target : Target)
+ redo()
+ toString() : String
+ undo()
}
class ShrinkSpell {
- oldSize : Size
- target : Target
+ ShrinkSpell()
+ execute(target : Target)
+ redo()
+ toString() : String
+ undo()
+ changeSize()
+ changeVisibility()
}
enum Size {
+ NORMAL {static}
@ -62,22 +40,19 @@ package com.iluwatar.command {
}
class Wizard {
- LOGGER : Logger {static}
- redoStack : Deque<Command>
- undoStack : Deque<Command>
- redoStack : Deque<Runnable>
- undoStack : Deque<Runnable>
+ Wizard()
+ castSpell(command : Command, target : Target)
+ castSpell(Runnable : runnable)
+ redoLastSpell()
+ toString() : String
+ undoLastSpell()
}
}
Target --> "-size" Size
Wizard --> "-undoStack" Command
ShrinkSpell --> "-oldSize" Size
InvisibilitySpell --> "-target" Target
ShrinkSpell --> "-target" Target
Wizard --> "-changeSize" Goblin
Wizard --> "-changeVisibility" Goblin
Target --> "-visibility" Visibility
Goblin --|> Target
InvisibilitySpell ..|> Command
ShrinkSpell ..|> Command
App --> "castSpell" Wizard
@enduml

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>command</artifactId>
<dependencies>

View File

@ -30,12 +30,10 @@ package com.iluwatar.command;
*
* <p>Four terms always associated with the command pattern are command, receiver, invoker and
* client. A command object (spell) knows about the receiver (target) and invokes a method of the
* receiver. Values for parameters of the receiver method are stored in the command. The receiver
* then does the work. An invoker object (wizard) knows how to execute a command, and optionally
* does bookkeeping about the command execution. The invoker does not know anything about a concrete
* command, it knows only about command interface. Both an invoker object and several command
* objects are held by a client object (app). The client decides which commands to execute at which
* points. To execute a command, it passes the command object to the invoker object.
* receiver. An invoker object (wizard) receives a reference to the command to be executed and
* optionally does bookkeeping about the command execution. The invoker does not know anything
* about how the command is executed. The client decides which commands to execute at which
* points. To execute a command, it passes a reference of the function to the invoker object.
*
* <p>In other words, in this example the wizard casts spells on the goblin. The wizard keeps track
* of the previous spells cast, so it is easy to undo them. In addition, the wizard keeps track of
@ -54,10 +52,10 @@ public class App {
goblin.printStatus();
wizard.castSpell(new ShrinkSpell(), goblin);
wizard.castSpell(goblin::changeSize);
goblin.printStatus();
wizard.castSpell(new InvisibilitySpell(), goblin);
wizard.castSpell(goblin::changeVisibility);
goblin.printStatus();
wizard.undoLastSpell();

View File

@ -37,5 +37,4 @@ public class Goblin extends Target {
public String toString() {
return "Goblin";
}
}

View File

@ -62,4 +62,21 @@ public abstract class Target {
public void printStatus() {
LOGGER.info("{}, [size={}] [visibility={}]", this, getSize(), getVisibility());
}
/**
* Changes the size of the target.
*/
public void changeSize() {
var oldSize = getSize() == Size.NORMAL ? Size.SMALL : Size.NORMAL;
setSize(oldSize);
}
/**
* Changes the visibility of the target.
*/
public void changeVisibility() {
var visible = getVisibility() == Visibility.INVISIBLE
? Visibility.VISIBLE : Visibility.INVISIBLE;
setVisibility(visible);
}
}

View File

@ -25,30 +25,24 @@ package com.iluwatar.command;
import java.util.Deque;
import java.util.LinkedList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Wizard is the invoker of the commands.
*/
public class Wizard {
private static final Logger LOGGER = LoggerFactory.getLogger(Wizard.class);
private final Deque<Command> undoStack = new LinkedList<>();
private final Deque<Command> redoStack = new LinkedList<>();
private final Deque<Runnable> undoStack = new LinkedList<>();
private final Deque<Runnable> redoStack = new LinkedList<>();
public Wizard() {
// comment to ignore sonar issue: LEVEL critical
}
/**
* Cast spell.
*/
public void castSpell(Command command, Target target) {
LOGGER.info("{} casts {} at {}", this, command, target);
command.execute(target);
undoStack.offerLast(command);
public void castSpell(Runnable runnable) {
runnable.run();
undoStack.offerLast(runnable);
}
/**
@ -58,8 +52,7 @@ public class Wizard {
if (!undoStack.isEmpty()) {
var previousSpell = undoStack.pollLast();
redoStack.offerLast(previousSpell);
LOGGER.info("{} undoes {}", this, previousSpell);
previousSpell.undo();
previousSpell.run();
}
}
@ -70,8 +63,7 @@ public class Wizard {
if (!redoStack.isEmpty()) {
var previousSpell = redoStack.pollLast();
undoStack.offerLast(previousSpell);
LOGGER.info("{} redoes {}", this, previousSpell);
previousSpell.redo();
previousSpell.run();
}
}

View File

@ -56,10 +56,10 @@ public class CommandTest {
var wizard = new Wizard();
var goblin = new Goblin();
wizard.castSpell(new ShrinkSpell(), goblin);
wizard.castSpell(goblin::changeSize);
verifyGoblin(goblin, GOBLIN, Size.SMALL, Visibility.VISIBLE);
wizard.castSpell(new InvisibilitySpell(), goblin);
wizard.castSpell(goblin::changeVisibility);
verifyGoblin(goblin, GOBLIN, Size.SMALL, Visibility.INVISIBLE);
wizard.undoLastSpell();

View File

@ -27,7 +27,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>commander</artifactId>
<dependencies>

View File

@ -9,15 +9,17 @@ tags:
---
## Intent
Compose objects into tree structures to represent part-whole
hierarchies. Composite lets clients treat individual objects and compositions
of objects uniformly.
Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients
treat individual objects and compositions of objects uniformly.
## Explanation
Real world example
> Every sentence is composed of words which are in turn composed of characters. Each of these objects is printable and they can have something printed before or after them like sentence always ends with full stop and word always has space before it
> Every sentence is composed of words which are in turn composed of characters. Each of these
> objects is printable and they can have something printed before or after them like sentence always
> ends with full stop and word always has space before it.
In plain words
@ -25,11 +27,16 @@ In plain words
Wikipedia says
> In software engineering, the composite pattern is a partitioning design pattern. The composite pattern describes that a group of objects is to be treated in the same way as a single instance of an object. The intent of a composite is to "compose" objects into tree structures to represent part-whole hierarchies. Implementing the composite pattern lets clients treat individual objects and compositions uniformly.
> In software engineering, the composite pattern is a partitioning design pattern. The composite
> pattern describes that a group of objects is to be treated in the same way as a single instance of
> an object. The intent of a composite is to "compose" objects into tree structures to represent
> part-whole hierarchies. Implementing the composite pattern lets clients treat individual objects
> and compositions uniformly.
**Programmatic Example**
Taking our sentence example from above. Here we have the base class and different printable types
Taking our sentence example from above. Here we have the base class `LetterComposite` and the
different printable types `Letter`, `Word` and `Sentence`.
```java
public abstract class LetterComposite {
@ -102,7 +109,7 @@ public class Sentence extends LetterComposite {
}
```
Then we have a messenger to carry messages
Then we have a messenger to carry messages:
```java
public class Messenger {
@ -143,7 +150,7 @@ public class Messenger {
}
```
And then it can be used as
And then it can be used as:
```java
var orcMessage = new Messenger().messageFromOrcs();
@ -153,13 +160,16 @@ elfMessage.print(); // Much wind pours from your mouth.
```
## Class diagram
![alt text](./etc/composite.urm.png "Composite class diagram")
## Applicability
Use the Composite pattern when
* you want to represent part-whole hierarchies of objects
* you want clients to be able to ignore the difference between compositions of objects and individual objects. Clients will treat all objects in the composite structure uniformly
* You want to represent part-whole hierarchies of objects.
* You want clients to be able to ignore the difference between compositions of objects and
individual objects. Clients will treat all objects in the composite structure uniformly.
## Real world examples

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>composite</artifactId>
<dependencies>

View File

@ -9,16 +9,19 @@ tags:
---
## Intent
The purpose of the Converter Pattern is to provide a generic, common way of bidirectional
The purpose of the Converter pattern is to provide a generic, common way of bidirectional
conversion between corresponding types, allowing a clean implementation in which the types do not
need to be aware of each other. Moreover, the Converter Pattern introduces bidirectional collection
need to be aware of each other. Moreover, the Converter pattern introduces bidirectional collection
mapping, reducing a boilerplate code to minimum.
## Explanation
Real world example
> In real world applications it is often the case that database layer consists of entities that need to be mapped into DTOs for use on the business logic layer. Similar mapping is done for potentially huge amount of classes and we need a generic way to achieve this.
> In real world applications it is often the case that database layer consists of entities that need
> to be mapped into DTOs for use on the business logic layer. Similar mapping is done for
> potentially huge amount of classes and we need a generic way to achieve this.
In plain words
@ -26,7 +29,8 @@ In plain words
**Programmatic Example**
We need a generic solution for the mapping problem. To achieve this, let's introduce a generic converter.
We need a generic solution for the mapping problem. To achieve this, let's introduce a generic
converter.
```java
public class Converter<T, U> {
@ -77,7 +81,7 @@ public class UserConverter extends Converter<UserDto, User> {
}
```
Now mapping between User and UserDto becomes trivial.
Now mapping between `User` and `UserDto` becomes trivial.
```java
var userConverter = new UserConverter();
@ -86,14 +90,18 @@ var user = userConverter.convertFromDto(dtoUser);
```
## Class diagram
![alt text](./etc/converter.png "Converter Pattern")
## Applicability
Use the Converter Pattern in the following situations:
* When you have types that logically correspond which other and you need to convert entities between them
* When you want to provide different ways of types conversions depending on a context
* Whenever you introduce a DTO (Data transfer object), you will probably need to convert it into the domain equivalence
* When you have types that logically correspond with each other and you need to convert entities
between them.
* When you want to provide different ways of types conversions depending on the context.
* Whenever you introduce a DTO (Data transfer object), you will probably need to convert it into the
domain equivalence.
## Credits

View File

@ -20,7 +20,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>converter</artifactId>
<modelVersion>4.0.0</modelVersion>

View File

@ -30,7 +30,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>cqrs</artifactId>
<dependencies>

View File

@ -9,13 +9,15 @@ tags:
---
## Intent
Object provides an abstract interface to some type of database or other persistence mechanism.
## Explanation
Real world example
> There's a set of customers that need to be persisted to database. Additionally we need the whole set of CRUD (create/read/update/delete) operations so we can operate on customers easily.
> There's a set of customers that need to be persisted to database. Additionally we need the whole
> set of CRUD (create/read/update/delete) operations so we can operate on customers easily.
In plain words
@ -23,11 +25,12 @@ In plain words
Wikipedia says
> In computer software, a data access object (DAO) is a pattern that provides an abstract interface to some type of database or other persistence mechanism.
> In computer software, a data access object (DAO) is a pattern that provides an abstract interface
> to some type of database or other persistence mechanism.
**Programmatic Example**
Walking through our customers example, here's the basic Customer entity.
Walking through our customers example, here's the basic `Customer` entity.
```java
public class Customer {
@ -41,60 +44,13 @@ public class Customer {
this.firstName = firstName;
this.lastName = lastName;
}
public int getId() {
return id;
}
public void setId(final int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(final String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(final String lastName) {
this.lastName = lastName;
}
@Override
public String toString() {
return "Customer{" + "id=" + getId() + ", firstName='" + getFirstName() + '\'' + ", lastName='"
+ getLastName() + '\'' + '}';
}
@Override
public boolean equals(final Object that) {
var isEqual = false;
if (this == that) {
isEqual = true;
} else if (that != null && getClass() == that.getClass()) {
final var customer = (Customer) that;
if (getId() == customer.getId()) {
isEqual = true;
}
}
return isEqual;
}
@Override
public int hashCode() {
return getId();
}
// getters and setters ->
...
}
```
Here's the DAO interface and two different implementations for it. InMemoryCustomerDao keeps a simple map of customers
in memory while DBCustomerDao is the real RDBMS implementation.
Here's the `CustomerDao` interface and two different implementations for it. `InMemoryCustomerDao`
keeps a simple map of customers in memory while `DBCustomerDao` is the real RDBMS implementation.
```java
public interface CustomerDao {
@ -114,35 +70,8 @@ public class InMemoryCustomerDao implements CustomerDao {
private final Map<Integer, Customer> idToCustomer = new HashMap<>();
@Override
public Stream<Customer> getAll() {
return idToCustomer.values().stream();
}
@Override
public Optional<Customer> getById(final int id) {
return Optional.ofNullable(idToCustomer.get(id));
}
@Override
public boolean add(final Customer customer) {
if (getById(customer.getId()).isPresent()) {
return false;
}
idToCustomer.put(customer.getId(), customer);
return true;
}
@Override
public boolean update(final Customer customer) {
return idToCustomer.replace(customer.getId(), customer) != null;
}
@Override
public boolean delete(final Customer customer) {
return idToCustomer.remove(customer.getId()) != null;
}
// implement the interface using the map
...
}
public class DbCustomerDao implements CustomerDao {
@ -155,121 +84,8 @@ public class DbCustomerDao implements CustomerDao {
this.dataSource = dataSource;
}
@Override
public Stream<Customer> getAll() throws Exception {
try {
var connection = getConnection();
var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS");
var resultSet = statement.executeQuery();
return StreamSupport.stream(new Spliterators.AbstractSpliterator<Customer>(Long.MAX_VALUE,
Spliterator.ORDERED) {
@Override
public boolean tryAdvance(Consumer<? super Customer> action) {
try {
if (!resultSet.next()) {
return false;
}
action.accept(createCustomer(resultSet));
return true;
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}, false).onClose(() -> mutedClose(connection, statement, resultSet));
} catch (SQLException e) {
throw new CustomException(e.getMessage(), e);
}
}
private Connection getConnection() throws SQLException {
return dataSource.getConnection();
}
private void mutedClose(Connection connection, PreparedStatement statement, ResultSet resultSet) {
try {
resultSet.close();
statement.close();
connection.close();
} catch (SQLException e) {
LOGGER.info("Exception thrown " + e.getMessage());
}
}
private Customer createCustomer(ResultSet resultSet) throws SQLException {
return new Customer(resultSet.getInt("ID"),
resultSet.getString("FNAME"),
resultSet.getString("LNAME"));
}
@Override
public Optional<Customer> getById(int id) throws Exception {
ResultSet resultSet = null;
try (var connection = getConnection();
var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS WHERE ID = ?")) {
statement.setInt(1, id);
resultSet = statement.executeQuery();
if (resultSet.next()) {
return Optional.of(createCustomer(resultSet));
} else {
return Optional.empty();
}
} catch (SQLException ex) {
throw new CustomException(ex.getMessage(), ex);
} finally {
if (resultSet != null) {
resultSet.close();
}
}
}
@Override
public boolean add(Customer customer) throws Exception {
if (getById(customer.getId()).isPresent()) {
return false;
}
try (var connection = getConnection();
var statement = connection.prepareStatement("INSERT INTO CUSTOMERS VALUES (?,?,?)")) {
statement.setInt(1, customer.getId());
statement.setString(2, customer.getFirstName());
statement.setString(3, customer.getLastName());
statement.execute();
return true;
} catch (SQLException ex) {
throw new CustomException(ex.getMessage(), ex);
}
}
@Override
public boolean update(Customer customer) throws Exception {
try (var connection = getConnection();
var statement =
connection
.prepareStatement("UPDATE CUSTOMERS SET FNAME = ?, LNAME = ? WHERE ID = ?")) {
statement.setString(1, customer.getFirstName());
statement.setString(2, customer.getLastName());
statement.setInt(3, customer.getId());
return statement.executeUpdate() > 0;
} catch (SQLException ex) {
throw new CustomException(ex.getMessage(), ex);
}
}
@Override
public boolean delete(Customer customer) throws Exception {
try (var connection = getConnection();
var statement = connection.prepareStatement("DELETE FROM CUSTOMERS WHERE ID = ?")) {
statement.setInt(1, customer.getId());
return statement.executeUpdate() > 0;
} catch (SQLException ex) {
throw new CustomException(ex.getMessage(), ex);
}
}
}
// implement the interface using the data source
...
```
Finally here's how we use our DAO to manage customers.
@ -301,15 +117,45 @@ Finally here's how we use our DAO to manage customers.
deleteSchema(dataSource);
```
The program output:
```java
customerDao.getAllCustomers():
Customer{id=1, firstName='Adam', lastName='Adamson'}
Customer{id=2, firstName='Bob', lastName='Bobson'}
Customer{id=3, firstName='Carl', lastName='Carlson'}
customerDao.getCustomerById(2): Optional[Customer{id=2, firstName='Bob', lastName='Bobson'}]
customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@7cef4e59
customerDao.getAllCustomers():
Customer{id=1, firstName='Adam', lastName='Adamson'}
Customer{id=2, firstName='Bob', lastName='Bobson'}
Customer{id=3, firstName='Carl', lastName='Carlson'}
Customer{id=4, firstName='Daniel', lastName='Danielson'}
customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@2db0f6b2
customerDao.getAllCustomers():
Customer{id=1, firstName='Adam', lastName='Adamson'}
Customer{id=2, firstName='Bob', lastName='Bobson'}
Customer{id=3, firstName='Carl', lastName='Carlson'}
customerDao.getCustomerById(2): Optional[Customer{id=2, firstName='Bob', lastName='Bobson'}]
customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@12c8a2c0
customerDao.getAllCustomers():
Customer{id=1, firstName='Adam', lastName='Adamson'}
Customer{id=2, firstName='Bob', lastName='Bobson'}
Customer{id=3, firstName='Carl', lastName='Carlson'}
Customer{id=4, firstName='Daniel', lastName='Danielson'}
customerDao.getAllCustomers(): java.util.stream.ReferencePipeline$Head@6ec8211c
```
## Class diagram
![alt text](./etc/dao.png "Data Access Object")
## Applicability
Use the Data Access Object in any of the following situations
* when you want to consolidate how the data layer is accessed
* when you want to avoid writing multiple data retrieval/persistence layers
Use the Data Access Object in any of the following situations:
* When you want to consolidate how the data layer is accessed.
* When you want to avoid writing multiple data retrieval/persistence layers.
## Credits

View File

@ -30,7 +30,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>dao</artifactId>

View File

@ -33,7 +33,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>data-bus</artifactId>
<dependencies>

View File

@ -30,7 +30,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>data-locality</artifactId>

View File

@ -28,7 +28,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>data-mapper</artifactId>
<dependencies>

View File

@ -9,13 +9,16 @@ tags:
---
## Intent
Pass data with multiple attributes in one shot from client to server, to avoid multiple calls to remote server.
Pass data with multiple attributes in one shot from client to server, to avoid multiple calls to
remote server.
## Explanation
Real world example
> We need to fetch information about customers from remote database. Instead of querying the attributes one at a time, we use DTOs to transfer all the relevant attributes in a single shot.
> We need to fetch information about customers from remote database. Instead of querying the
> attributes one at a time, we use DTOs to transfer all the relevant attributes in a single shot.
In plain words
@ -23,16 +26,17 @@ In plain words
Wikipedia says
> In the field of programming a data transfer object (DTO) is an object that carries data between processes. The
motivation for its use is that communication between processes is usually done resorting to remote interfaces
(e.g., web services), where each call is an expensive operation. Because the majority of the cost of each call is
related to the round-trip time between the client and the server, one way of reducing the number of calls is to use an
object (the DTO) that aggregates the data that would have been transferred by the several calls, but that is served by
one call only.
> In the field of programming a data transfer object (DTO) is an object that carries data between
> processes. The motivation for its use is that communication between processes is usually done
> resorting to remote interfaces (e.g. web services), where each call is an expensive operation.
> Because the majority of the cost of each call is related to the round-trip time between the client
> and the server, one way of reducing the number of calls is to use an object (the DTO) that
> aggregates the data that would have been transferred by the several calls, but that is served by
> one call only.
**Programmatic Example**
Let's first introduce our simple customer DTO class.
Let's first introduce our simple `CustomerDTO` class.
```java
public class CustomerDto {
@ -60,7 +64,7 @@ public class CustomerDto {
}
```
Customer resource class acts as the server for customer information.
`CustomerResource` class acts as the server for customer information.
```java
public class CustomerResource {
@ -94,10 +98,12 @@ Now fetching customer information is easy since we have the DTOs.
```
## Class diagram
![alt text](./etc/data-transfer-object.urm.png "data-transfer-object")
## Applicability
Use the Data Transfer Object pattern when
Use the Data Transfer Object pattern when:
* The client is asking for multiple information. And the information is related.
* When you want to boost the performance to get resources.

View File

@ -28,7 +28,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>data-transfer-object</artifactId>
<dependencies>

View File

@ -23,7 +23,13 @@
package com.iluwatar.datatransfer;
import com.iluwatar.datatransfer.customer.CustomerDto;
import com.iluwatar.datatransfer.customer.CustomerResource;
import com.iluwatar.datatransfer.product.Product;
import com.iluwatar.datatransfer.product.ProductDto;
import com.iluwatar.datatransfer.product.ProductResource;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@ -32,11 +38,17 @@ import org.slf4j.LoggerFactory;
* The Data Transfer Object pattern is a design pattern in which an data transfer object is used to
* serve related information together to avoid multiple call for each piece of information.
*
* <p>In this example, ({@link App}) as as customer details consumer i.e. client to
* request for customer details to server.
* <p>In the first example, {@link App} is a customer details consumer i.e. client to
* request for customer details to server. {@link CustomerResource} act as server to serve customer
* information. {@link CustomerDto} is data transfer object to share customer information.
*
* <p>In the second example, {@link App} is a product details consumer i.e. client to
* request for product details to server. {@link ProductResource} acts as server to serve
* product information. {@link ProductDto} is data transfer object to share product information.
*
* <p>The pattern implementation is a bit different in each of the examples. The first can be
* thought as a traditional example and the second is an enum based implementation.
*
* <p>CustomerResource ({@link CustomerResource}) act as server to serve customer information. And
* The CustomerDto ({@link CustomerDto} is data transfer object to share customer information.
*/
public class App {
@ -48,6 +60,8 @@ public class App {
* @param args program argument.
*/
public static void main(String[] args) {
// Example 1: Customer DTO
var customerOne = new CustomerDto("1", "Kelly", "Brown");
var customerTwo = new CustomerDto("2", "Alfonso", "Bass");
var customers = new ArrayList<>(List.of(customerOne, customerTwo));
@ -72,6 +86,53 @@ public class App {
customerResource.save(customerThree);
allCustomers = customerResource.getAllCustomers();
printCustomerDetails(allCustomers);
// Example 2: Product DTO
Product tv =
new Product().setId(1L).setName("TV").setSupplier("Sony").setPrice(1000D).setCost(1090D);
Product microwave =
new Product()
.setId(2L)
.setName("microwave")
.setSupplier("Delonghi")
.setPrice(1000D)
.setCost(1090D);
Product refrigerator =
new Product()
.setId(3L)
.setName("refrigerator")
.setSupplier("Botsch")
.setPrice(1000D)
.setCost(1090D);
Product airConditioner =
new Product()
.setId(4L)
.setName("airConditioner")
.setSupplier("LG")
.setPrice(1000D)
.setCost(1090D);
List<Product> products =
new ArrayList<>(Arrays.asList(tv, microwave, refrigerator, airConditioner));
ProductResource productResource = new ProductResource(products);
LOGGER.info(
"####### List of products including sensitive data just for admins: \n {}",
Arrays.toString(productResource.getAllProductsForAdmin().toArray()));
LOGGER.info(
"####### List of products for customers: \n {}",
Arrays.toString(productResource.getAllProductsForCustomer().toArray()));
LOGGER.info("####### Going to save Sony PS5 ...");
ProductDto.Request.Create createProductRequestDto =
new ProductDto.Request.Create()
.setName("PS5")
.setCost(1000D)
.setPrice(1220D)
.setSupplier("Sony");
productResource.save(createProductRequestDto);
LOGGER.info(
"####### List of products after adding PS5: {}",
Arrays.toString(productResource.getProducts().toArray()));
}
private static void printCustomerDetails(List<CustomerDto> allCustomers) {

View File

@ -21,7 +21,7 @@
* THE SOFTWARE.
*/
package com.iluwatar.datatransfer;
package com.iluwatar.datatransfer.customer;
/**
* {@link CustomerDto} is a data transfer object POJO. Instead of sending individual information to

View File

@ -21,7 +21,7 @@
* THE SOFTWARE.
*/
package com.iluwatar.datatransfer;
package com.iluwatar.datatransfer.customer;
import java.util.List;

View File

@ -0,0 +1,114 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.datatransfer.product;
/**
* {@link Product} is a entity class for product entity. This class act as entity in the demo.
*/
public final class Product {
private Long id;
private String name;
private Double price;
private Double cost;
private String supplier;
/**
* Constructor.
*
* @param id product id
* @param name product name
* @param price product price
* @param cost product cost
* @param supplier product supplier
*/
public Product(Long id, String name, Double price, Double cost, String supplier) {
this.id = id;
this.name = name;
this.price = price;
this.cost = cost;
this.supplier = supplier;
}
/**
* Constructor.
*/
public Product() {
}
public Long getId() {
return id;
}
public Product setId(Long id) {
this.id = id;
return this;
}
public String getName() {
return name;
}
public Product setName(String name) {
this.name = name;
return this;
}
public Double getPrice() {
return price;
}
public Product setPrice(Double price) {
this.price = price;
return this;
}
public Double getCost() {
return cost;
}
public Product setCost(Double cost) {
this.cost = cost;
return this;
}
public String getSupplier() {
return supplier;
}
public Product setSupplier(String supplier) {
this.supplier = supplier;
return this;
}
@Override
public String toString() {
return "Product{"
+ "id=" + id
+ ", name='" + name + '\''
+ ", price=" + price
+ ", cost=" + cost
+ ", supplier='" + supplier + '\''
+ '}';
}
}

View File

@ -0,0 +1,287 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.datatransfer.product;
/**
* {@link ProductDto} is a data transfer object POJO.
* Instead of sending individual information to
* client We can send related information together in POJO.
*
* <p>Dto will not have any business logic in it.
*/
public enum ProductDto {
;
/**
* This is Request class which consist of Create or any other request DTO's
* you might want to use in your API.
*/
public enum Request {
;
/**
* This is Create dto class for requesting create new product.
*/
public static final class Create implements Name, Price, Cost, Supplier {
private String name;
private Double price;
private Double cost;
private String supplier;
@Override
public String getName() {
return name;
}
public Create setName(String name) {
this.name = name;
return this;
}
@Override
public Double getPrice() {
return price;
}
public Create setPrice(Double price) {
this.price = price;
return this;
}
@Override
public Double getCost() {
return cost;
}
public Create setCost(Double cost) {
this.cost = cost;
return this;
}
@Override
public String getSupplier() {
return supplier;
}
public Create setSupplier(String supplier) {
this.supplier = supplier;
return this;
}
}
}
/**
* This is Response class which consist of any response DTO's
* you might want to provide to your clients.
*/
public enum Response {
;
/**
* This is Public dto class for API response with the lowest data security.
*/
public static final class Public implements Id, Name, Price {
private Long id;
private String name;
private Double price;
@Override
public Long getId() {
return id;
}
public Public setId(Long id) {
this.id = id;
return this;
}
@Override
public String getName() {
return name;
}
public Public setName(String name) {
this.name = name;
return this;
}
@Override
public Double getPrice() {
return price;
}
public Public setPrice(Double price) {
this.price = price;
return this;
}
@Override
public String toString() {
return "Public{"
+ "id="
+ id
+ ", name='"
+ name
+ '\''
+ ", price="
+ price
+ '}';
}
}
/**
* This is Private dto class for API response with the highest data security.
*/
public static final class Private implements Id, Name, Price, Cost {
private Long id;
private String name;
private Double price;
private Double cost;
@Override
public Long getId() {
return id;
}
public Private setId(Long id) {
this.id = id;
return this;
}
@Override
public String getName() {
return name;
}
public Private setName(String name) {
this.name = name;
return this;
}
@Override
public Double getPrice() {
return price;
}
public Private setPrice(Double price) {
this.price = price;
return this;
}
@Override
public Double getCost() {
return cost;
}
public Private setCost(Double cost) {
this.cost = cost;
return this;
}
@Override
public String toString() {
return "Private{"
+
"id="
+ id
+
", name='"
+ name
+ '\''
+
", price="
+ price
+
", cost="
+ cost
+
'}';
}
}
}
/**
* Use this interface whenever you want to provide the product Id in your DTO.
*/
private interface Id {
/**
* Unique identifier of the product.
*
* @return : id of the product.
*/
Long getId();
}
/**
* Use this interface whenever you want to provide the product Name in your DTO.
*/
private interface Name {
/**
* The name of the product.
*
* @return : name of the product.
*/
String getName();
}
/**
* Use this interface whenever you want to provide the product Price in your DTO.
*/
private interface Price {
/**
* The amount we sell a product for.
* <b>This data is not confidential</b>
*
* @return : price of the product.
*/
Double getPrice();
}
/**
* Use this interface whenever you want to provide the product Cost in your DTO.
*/
private interface Cost {
/**
* The amount that it costs us to purchase this product
* For the amount we sell a product for, see the {@link Price Price} parameter.
* <b>This data is confidential</b>
*
* @return : cost of the product.
*/
Double getCost();
}
/**
* Use this interface whenever you want to provide the product Supplier in your DTO.
*/
private interface Supplier {
/**
* The name of supplier of the product or its manufacturer.
* <b>This data is highly confidential</b>
*
* @return : supplier of the product.
*/
String getSupplier();
}
}

View File

@ -0,0 +1,94 @@
/*
* The MIT License
* Copyright © 2014-2019 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.datatransfer.product;
import java.util.List;
import java.util.stream.Collectors;
/**
* The resource class which serves product information. This class act as server in the demo. Which
* has all product details.
*/
public class ProductResource {
private final List<Product> products;
/**
* Initialise resource with existing products.
*
* @param products initialize resource with existing products. Act as database.
*/
public ProductResource(final List<Product> products) {
this.products = products;
}
/**
* Get all products.
*
* @return : all products in list but in the scheme of private dto.
*/
public List<ProductDto.Response.Private> getAllProductsForAdmin() {
return products
.stream()
.map(p -> new ProductDto.Response.Private().setId(p.getId()).setName(p.getName())
.setCost(p.getCost())
.setPrice(p.getPrice()))
.collect(Collectors.toList());
}
/**
* Get all products.
*
* @return : all products in list but in the scheme of public dto.
*/
public List<ProductDto.Response.Public> getAllProductsForCustomer() {
return products
.stream()
.map(p -> new ProductDto.Response.Public().setId(p.getId()).setName(p.getName())
.setPrice(p.getPrice()))
.collect(Collectors.toList());
}
/**
* Save new product.
*
* @param createProductDto save new product to list.
*/
public void save(ProductDto.Request.Create createProductDto) {
products.add(new Product()
.setId((long) (products.size() + 1))
.setName(createProductDto.getName())
.setSupplier(createProductDto.getSupplier())
.setPrice(createProductDto.getPrice())
.setCost(createProductDto.getCost()));
}
/**
* List of all products in an entity representation.
*
* @return : all the products entity that stored in the products list
*/
public List<Product> getProducts() {
return products;
}
}

View File

@ -21,13 +21,16 @@
* THE SOFTWARE.
*/
package com.iluwatar.datatransfer;
package com.iluwatar.datatransfer.customer;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;
import java.util.ArrayList;
import java.util.List;
import com.iluwatar.datatransfer.customer.CustomerDto;
import com.iluwatar.datatransfer.customer.CustomerResource;
import org.junit.jupiter.api.Test;
/**

View File

@ -10,30 +10,39 @@ tags:
---
## Also known as
Wrapper
## Intent
Attach additional responsibilities to an object dynamically.
Decorators provide a flexible alternative to subclassing for extending
functionality.
Attach additional responsibilities to an object dynamically. Decorators provide a flexible
alternative to subclassing for extending functionality.
## Explanation
Real world example
> There is an angry troll living in the nearby hills. Usually it goes bare handed but sometimes it has a weapon. To arm the troll it's not necessary to create a new troll but to decorate it dynamically with a suitable weapon.
> There is an angry troll living in the nearby hills. Usually it goes bare handed but sometimes it
> has a weapon. To arm the troll it's not necessary to create a new troll but to decorate it
> dynamically with a suitable weapon.
In plain words
> Decorator pattern lets you dynamically change the behavior of an object at run time by wrapping them in an object of a decorator class.
> Decorator pattern lets you dynamically change the behavior of an object at run time by wrapping
> them in an object of a decorator class.
Wikipedia says
> In object-oriented programming, the decorator pattern is a design pattern that allows behavior to be added to an individual object, either statically or dynamically, without affecting the behavior of other objects from the same class. The decorator pattern is often useful for adhering to the Single Responsibility Principle, as it allows functionality to be divided between classes with unique areas of concern.
> In object-oriented programming, the decorator pattern is a design pattern that allows behavior to
> be added to an individual object, either statically or dynamically, without affecting the behavior
> of other objects from the same class. The decorator pattern is often useful for adhering to the
> Single Responsibility Principle, as it allows functionality to be divided between classes with
> unique areas of concern.
**Programmatic Example**
Let's take the troll example. First of all we have a simple troll implementing the troll interface
Let's take the troll example. First of all we have a `SimpleTroll` implementing the `Troll`
interface:
```java
public interface Troll {
@ -63,7 +72,7 @@ public class SimpleTroll implements Troll {
}
```
Next we want to add club for the troll. We can do it dynamically by using a decorator
Next we want to add club for the troll. We can do it dynamically by using a decorator:
```java
public class ClubbedTroll implements Troll {
@ -94,7 +103,7 @@ public class ClubbedTroll implements Troll {
}
```
Here's the troll in action
Here's the troll in action:
```java
// simple troll
@ -108,20 +117,36 @@ clubbedTroll.attack(); // The troll tries to grab you! The troll swings at you w
clubbedTroll.fleeBattle(); // The troll shrieks in horror and runs away!
```
Program output:
```java
The troll tries to grab you!
The troll shrieks in horror and runs away!
The troll tries to grab you! The troll swings at you with a club!
The troll shrieks in horror and runs away!
```
## Class diagram
![alt text](./etc/decorator.urm.png "Decorator pattern class diagram")
## Applicability
Use Decorator
* To add responsibilities to individual objects dynamically and transparently, that is, without affecting other objects
* For responsibilities that can be withdrawn
* When extension by subclassing is impractical. Sometimes a large number of independent extensions are possible and would produce an explosion of subclasses to support every combination. Or a class definition may be hidden or otherwise unavailable for subclassing
Decorator is used to:
* Add responsibilities to individual objects dynamically and transparently, that is, without
affecting other objects.
* For responsibilities that can be withdrawn.
* When extension by subclassing is impractical. Sometimes a large number of independent extensions
are possible and would produce an explosion of subclasses to support every combination. Or a class
definition may be hidden or otherwise unavailable for subclassing.
## Tutorial
* [Decorator Pattern Tutorial](https://www.journaldev.com/1540/decorator-design-pattern-in-java-example)
## Real world examples
* [java.io.InputStream](http://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html), [java.io.OutputStream](http://docs.oracle.com/javase/8/docs/api/java/io/OutputStream.html),
[java.io.Reader](http://docs.oracle.com/javase/8/docs/api/java/io/Reader.html) and [java.io.Writer](http://docs.oracle.com/javase/8/docs/api/java/io/Writer.html)
* [java.util.Collections#synchronizedXXX()](http://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#synchronizedCollection-java.util.Collection-)

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>decorator</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -9,15 +9,19 @@ tags:
---
## Intent
Dependency Injection is a software design pattern in which one or more dependencies (or services) are injected, or
passed by reference, into a dependent object (or client) and are made part of the client's state. The pattern separates
the creation of a client's dependencies from its own behavior, which allows program designs to be loosely coupled and
to follow the inversion of control and single responsibility principles.
Dependency Injection is a software design pattern in which one or more dependencies (or services)
are injected, or passed by reference, into a dependent object (or client) and are made part of the
client's state. The pattern separates the creation of a client's dependencies from its own behavior,
which allows program designs to be loosely coupled and to follow the inversion of control and single
responsibility principles.
## Explanation
Real world example
> The old wizard likes to fill his pipe and smoke tobacco once in a while. However, he doesn't want to depend on a single tobacco brand only but likes to be able to enjoy them all interchangeably.
> The old wizard likes to fill his pipe and smoke tobacco once in a while. However, he doesn't want
> to depend on a single tobacco brand only but likes to be able to enjoy them all interchangeably.
In plain words
@ -25,11 +29,12 @@ In plain words
Wikipedia says
> In software engineering, dependency injection is a technique in which an object receives other objects that it depends on. These other objects are called dependencies.
> In software engineering, dependency injection is a technique in which an object receives other
> objects that it depends on. These other objects are called dependencies.
**Programmatic Example**
Let's first introduce the tobacco brands.
Let's first introduce the `Tobacco` interface and the concrete brands.
```java
public abstract class Tobacco {
@ -52,7 +57,7 @@ public class OldTobyTobacco extends Tobacco {
}
```
Next here's the wizard class hierarchy.
Next here's the `Wizard` class hierarchy.
```java
public interface Wizard {
@ -83,13 +88,15 @@ And lastly we can show how easy it is to give the old wizard any brand of tobacc
```
## Class diagram
![alt text](./etc/dependency-injection.png "Dependency Injection")
## Applicability
Use the Dependency Injection pattern when
* When you need to remove knowledge of concrete implementation from object
* To enable unit testing of classes in isolation using mock objects or stubs
Use the Dependency Injection pattern when:
* When you need to remove knowledge of concrete implementation from object.
* To enable unit testing of classes in isolation using mock objects or stubs.
## Credits

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>dependency-injection</artifactId>
<dependencies>

View File

@ -29,10 +29,10 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>dirty-flag</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
<name>dirty-flag</name>
<url>http://maven.apache.org</url>
<properties>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -27,7 +27,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>double-checked-locking</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.23.0-SNAPSHOT</version>
<version>1.24.0-SNAPSHOT</version>
</parent>
<artifactId>double-dispatch</artifactId>
<dependencies>

View File

@ -45,7 +45,7 @@ public class SpaceStationMir extends GameObject {
@Override
public void collisionResolve(FlamingAsteroid asteroid) {
LOGGER.info(AppConstants.HITS, " {} is damaged! {} is set on fire!", asteroid.getClass()
LOGGER.info(AppConstants.HITS + " {} is damaged! {} is set on fire!", asteroid.getClass()
.getSimpleName(),
this.getClass().getSimpleName(), this.getClass().getSimpleName(), this.getClass()
.getSimpleName());
@ -55,14 +55,14 @@ public class SpaceStationMir extends GameObject {
@Override
public void collisionResolve(Meteoroid meteoroid) {
LOGGER.info(AppConstants.HITS, " {} is damaged!", meteoroid.getClass().getSimpleName(),
LOGGER.info(AppConstants.HITS + " {} is damaged!", meteoroid.getClass().getSimpleName(),
this.getClass().getSimpleName(), this.getClass().getSimpleName());
setDamaged(true);
}
@Override
public void collisionResolve(SpaceStationMir mir) {
LOGGER.info(AppConstants.HITS, " {} is damaged!", mir.getClass().getSimpleName(),
LOGGER.info(AppConstants.HITS + " {} is damaged!", mir.getClass().getSimpleName(),
this.getClass().getSimpleName(), this.getClass().getSimpleName());
setDamaged(true);
}

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