21 lines
750 B
Markdown
21 lines
750 B
Markdown
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---
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layout: pattern
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title: Callback
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folder: callback
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categories: pattern_cat
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tags: pattern_tag
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---
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**Intent:** 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:** 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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