java-design-patterns/callback/README.md

---
layout: pattern
title: Callback
folder: callback
permalink: /patterns/callback/
categories: Other
tags:
 - Java
 - Difficulty-Beginner
 - Functional
 - Idiom
---

## 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.

## 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.
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: Callback`
			`folder: callback`
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/callback/`
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: Other`
Categorize and tag all patterns #213 2015-12-28 15:52:44 +02:00			`tags:`
			`- Java`
			`- Difficulty-Beginner`
			`- Functional`
			`- Idiom`
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`
			`Callback is a piece of executable code that is passed as an`
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			`argument to other code, which is expected to call back (execute) the argument`
			`at some convenient time.`

#1113 Link uml-reverse-mapper created class diagrams to readme, where needed 2019-12-07 20:01:13 +02:00			`## Class diagram`
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			`![alt text](./etc/callback.png "Callback")`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Applicability`
			`Use the Callback pattern when`
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
			`* when some arbitrary synchronous or asynchronous action must be performed after execution of some defined activity.`

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
Fix display error 2016-04-15 08:21:29 +03:00			`* [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.`