Future 和 Promise 有什么区别? [英] What's the difference between a Future and a Promise?

问题描述

Future 和 Promise 有什么区别?
它们都充当未来结果的占位符，但主要区别在哪里?

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

推荐答案

根据 this讨论，Promise 最终被称为 CompletableFuture 以包含在 Java 8 中，并且 它的 javadoc 解释说:

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

可以明确完成的 Future(设置其值和状态)，并且可以用作 CompletionStage，支持在其完成时触发的依赖功能和操作.

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.

列表中还给出了一个例子:

An example is also given on the list:

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

请注意，最终的 API 略有不同，但允许类似的异步执行:

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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