java-design-patterns/flyweight/README.md

---
layout: pattern
title: Flyweight
folder: flyweight
permalink: /patterns/flyweight/
pumlid: HSV94S8m3030Lg20M7-w4OvYAoCh7Xtnq3ty-Eq-MQlaJcdow17JNm26gpIEdkzqidffa4Qfrm2MN1XeSEADsqxEJRU94MJgCD1_W4C-YxZr08hwNqaRPUQGBm00
categories: Structural
tags:
 - Java
 - Gang Of Four
 - Difficulty-Intermediate
 - Performance
---

## Intent
Use sharing to support large numbers of fine-grained objects
efficiently.

![alt text](./etc/flyweight_1.png "Flyweight")

## Applicability
The Flyweight pattern's effectiveness depends heavily on how
and where it's used. Apply the Flyweight pattern when all of the following are
true

* an application uses a large number of objects
* storage costs are high because of the sheer quantity of objects
* most object state can be made extrinsic
* many groups of objects may be replaced by relatively few shared objects once extrinsic state is removed
* the application doesn't depend on object identity. Since flyweight objects may be shared, identity tests will return true for conceptually distinct objects.

## Real world examples

* [java.lang.Integer#valueOf(int)](http://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#valueOf%28int%29) and similarly for Byte, Character and other wrapped types.

## Credits

* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`---`
			`layout: pattern`
			`title: Flyweight`
			`folder: flyweight`
Work towards #56: Add permalink to every pattern This makes cleaner URLs thanks to jekyll 2015-08-15 18:03:05 +02:00			`permalink: /patterns/flyweight/`
Work on #190: Commit initial pumlId's added by the script 2016-08-30 15:10:34 +02:00			`pumlid: HSV94S8m3030Lg20M7-w4OvYAoCh7Xtnq3ty-Eq-MQlaJcdow17JNm26gpIEdkzqidffa4Qfrm2MN1XeSEADsqxEJRU94MJgCD1_W4C-YxZr08hwNqaRPUQGBm00`
Work on #213 - properly categorize all patterns - remove pattern list from readme - minor fixes to readme - removed "introduction" because its not a pattern and an error i committed some time ago 2015-08-20 21:40:07 +02:00			`categories: Structural`
#211 added further examples for structural and behavioral patterns 2016-08-20 20:49:28 +05:30			`tags:`
Work on #226, #213, added references of Gang Of Four to all GoF patterns, added tag for Gang Of Four, added difficulty tags to some of them 2015-09-22 18:25:56 +05:30			`- Java`
			`- Gang Of Four`
Categorize and tag all patterns #213 2015-12-28 15:52:44 +02:00			`- Difficulty-Intermediate`
Add performance tag to relevant patterns #213 2015-12-28 16:07:43 +02:00			`- Performance`
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`---`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Intent`
			`Use sharing to support large numbers of fine-grained objects`
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`efficiently.`

			`![alt text](./etc/flyweight_1.png "Flyweight")`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Applicability`
			`The Flyweight pattern's effectiveness depends heavily on how`
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`and where it's used. Apply the Flyweight pattern when all of the following are`
			`true`
Jekyll does not like enumerations w/o blank lines 2015-09-03 16:22:26 +02:00
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`* an application uses a large number of objects`
			`* storage costs are high because of the sheer quantity of objects`
			`* most object state can be made extrinsic`
			`* many groups of objects may be replaced by relatively few shared objects once extrinsic state is removed`
			`* the application doesn't depend on object identity. Since flyweight objects may be shared, identity tests will return true for conceptually distinct objects.`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Real world examples`
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00
#211 added further examples for structural and behavioral patterns 2016-08-20 20:49:28 +05:30			`* [java.lang.Integer#valueOf(int)](http://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#valueOf%28int%29) and similarly for Byte, Character and other wrapped types.`
Work on #226, #213, added references of Gang Of Four to all GoF patterns, added tag for Gang Of Four, added difficulty tags to some of them 2015-09-22 18:25:56 +05:30
Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Credits`
Work on #226, #213, added references of Gang Of Four to all GoF patterns, added tag for Gang Of Four, added difficulty tags to some of them 2015-09-22 18:25:56 +05:30
			`* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)`