30 lines
940 B
Markdown
30 lines
940 B
Markdown
---
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layout: pattern
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title: Callback
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folder: callback
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permalink: /patterns/callback/
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pumlid: FSVB4S8m30N0Lg20M7UwUL4qYOciUFGXxSE9s-wp6sjjKgwF8tF6YyXnjxtdKMk5E5-MOjdu6jIrRYIStlXWsIJwRij4fhW53SGFn51TmIT9yZ-jVBHPGxy0
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categories: Other
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tags:
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- Java
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- Difficulty-Beginner
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- Functional
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- Idiom
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---
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## Intent
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Callback is a piece of executable code that is passed as an
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argument to other code, which is expected to call back (execute) the argument
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at some convenient time.
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## Applicability
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Use the Callback pattern when
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* when some arbitrary synchronous or asynchronous action must be performed after execution of some defined activity.
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## Real world examples
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* [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.
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