java-design-patterns/decorator/index.md

---
layout: pattern
title: Decorator
folder: decorator
permalink: /patterns/decorator/
categories: Structural
tags: Java
---

**Intent:** Attach additional responsibilities to an object dynamically.
Decorators provide a flexible alternative to subclassing for extending
functionality.

![alt text](./etc/decorator_1.png "Decorator")

**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* for responsibilities that can be withdrawn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
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: Decorator`
			`folder: decorator`
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/decorator/`
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`
			`tags: Java`
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			`---`

			`Intent: Attach additional responsibilities to an object dynamically.`
			`Decorators provide a flexible alternative to subclassing for extending`
			`functionality.`

			`![alt text](./etc/decorator_1.png "Decorator")`

			`Applicability: Use Decorator`

			`* to add responsibilities to individual objects dynamically and transparently, that is, without affecting other objects`
			`* for responsibilities that can be withdrawn`
Work towards #56: Add permalink to every pattern This makes cleaner URLs thanks to jekyll 2015-08-15 18:03:05 +02:00			`* 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`