2aa9e78ddd
* Made minor changes in some patterns such as removed throws clause where not needed, changed incorrect order of arguments in assertEquals * Minor refactorings and code style changes. 1) Removed several use of raw types 2) Removed unnecessary throws clauses 3) Used lambda expressions wherever applicable 4) Used apt assertion methods for readability 5) Use of try with resources wherever applicable 6) Corrected incorrect order of assertXXX arguments * Removed unused import from Promise * Addressed review comments * Addressed checkstyle issue
layout, title, folder, permalink, categories, tags
| layout | title | folder | permalink | categories | tags | ||||
|---|---|---|---|---|---|---|---|---|---|
| pattern | Promise | promise | /patterns/promise/ | Concurrency |
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Also known as
CompletableFuture
Intent
A Promise represents a proxy for a value not necessarily known when the promise is created. It allows you to associate dependent promises to an asynchronous action's eventual success value or failure reason. Promises are a way to write async code that still appears as though it is executing in a synchronous way.
Applicability
Promise pattern is applicable in concurrent programming when some work needs to be done asynchronously and:
- code maintainability and readability suffers due to callback hell.
- you need to compose promises and need better error handling for asynchronous tasks.
- you want to use functional style of programming.
Real world examples
Related Patterns
- Async Method Invocation
- Callback