java-design-patterns/callback/index.md

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layout	title	folder	permalink	categories	tags
pattern	Callback	callback	/patterns/callback/	pattern_cat	pattern_tag

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.

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.