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task: Explanations and grammar fixes for all the GoF patterns (#1791)

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* Grammatical fixes to command pattern

* Update bridge pattern readme

* Fixes to builder pattern grammar

* Update chain of responsibility

* Improvements to the composite example

* Fixes to headings

* Minor updates to decorator pattern

* Update facade

* Update factory example

* Update factory method

* Update flyweight

* Interpreter explanation

* Update iterator readme

* Add explanation for mediator pattern

* Grammatical fixes to memento

* Grammar fixes for observer

* Update explanation for the prototype pattern

* Proxy pattern grammar fixes

* Update singleton

* Grammar fixes to state pattern

* Grammar fixes for strategy

* Grammar fixes, template method

* Grammar fixes for visitor

* Fix typo
This commit is contained in:
Ilkka Seppälä
2021-06-24 15:57:20 +03:00
committed by GitHub
parent bbdff14a66
commit 04bf566dc1
66 changed files with 872 additions and 357 deletions
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27
singleton/README.md
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@ -13,13 +13,12 @@ tags:
Ensure a class only has one instance, and provide a global point of access to it.
## Explanation
Real world example
Real-world example
> There can only be one ivory tower where the wizards study their magic. The same enchanted ivory
> tower is always used by the wizards. Ivory tower here is singleton.
> tower is always used by the wizards. The ivory tower here is a singleton.
In plain words
@ -46,9 +45,17 @@ public enum EnumIvoryTower {
Then in order to use:
```java
var enumIvoryTower1 = EnumIvoryTower.INSTANCE;
var enumIvoryTower2 = EnumIvoryTower.INSTANCE;
assertEquals(enumIvoryTower1, enumIvoryTower2); // true
var enumIvoryTower1 = EnumIvoryTower.INSTANCE;
var enumIvoryTower2 = EnumIvoryTower.INSTANCE;
LOGGER.info("enumIvoryTower1={}", enumIvoryTower1);
LOGGER.info("enumIvoryTower2={}", enumIvoryTower2);
```
The console output
```
enumIvoryTower1=com.iluwatar.singleton.EnumIvoryTower@1221555852
enumIvoryTower2=com.iluwatar.singleton.EnumIvoryTower@1221555852
```
## Class diagram
@ -62,13 +69,13 @@ Use the Singleton pattern when
* There must be exactly one instance of a class, and it must be accessible to clients from a well-known access point
* When the sole instance should be extensible by subclassing, and clients should be able to use an extended instance without modifying their code
## Typical Use Case
Some typical use cases for the Singleton
* The logging class
* Managing a connection to a database
* File manager
## Real world examples
## Known uses
* [java.lang.Runtime#getRuntime()](http://docs.oracle.com/javase/8/docs/api/java/lang/Runtime.html#getRuntime%28%29)
* [java.awt.Desktop#getDesktop()](http://docs.oracle.com/javase/8/docs/api/java/awt/Desktop.html#getDesktop--)
@ -77,8 +84,8 @@ Use the Singleton pattern when
## Consequences
* Violates Single Responsibility Principle (SRP) by controlling their own creation and lifecycle.
* Encourages using a global shared instance which prevents an object and resources used by this object from being deallocated.
* Violates Single Responsibility Principle (SRP) by controlling their creation and lifecycle.
* Encourages using a globally shared instance which prevents an object and resources used by this object from being deallocated.
* Creates tightly coupled code. The clients of the Singleton become difficult to test.
* Makes it almost impossible to subclass a Singleton.