未来与承诺的区别 [英] Difference between Future and Promise

问题描述

未来和 promise之间有什么区别？？

它们都像预留位置

根据 .edu / pipermail / concurrency-interest / 2012-December / 010423.html>此讨论， Promise 终于被调用 CompletableFuture 以包含在Java 8中，以及其javadoc 解释：

未来可以明确完成（设置其值和状态），并可用作完成区，支持完成后触发的依赖函数和动作。

列表中也列出了一个示例：

  f.then（（s  - > aStringFunction）.sasAsync（s  - > ...）; 
  

请注意，最终的API略有不同，但允许类似的异步执行：

  CompletableFuture ; String> f = ...; 
 f.thenApply（this :: modifyString）.thenAccept（System.out :: println）; 
  

What's the difference between future and promise?
They both act like a placeholder for future results, but where is the main difference?

解决方案

According to this discussion, Promise has finally been called CompletableFuture for inclusion in Java 8, and its javadoc explains:

A Future that may be explicitly completed (setting its value and status), and may be used as a CompletionStage, supporting dependent functions and actions that trigger upon its completion.

An example is also given on the list:

f.then((s -> aStringFunction(s)).thenAsync(s -> ...);

Note that the final API is slightly different but allows similar asynchronous execution:

CompletableFuture<String> f = ...;
f.thenApply(this::modifyString).thenAccept(System.out::println);

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