java - CompletableFuture.allOf().orTimeout() 的意外行为

Question

有两种方法可以强制执行 CompletableFuture 在给定的时间后超时:

orTimeout(long timeout, TimeUnit unit)

get(long timeout, TimeUnit unit)

我希望他们表现得一样。但是，当应用于 CompletableFuture.allOf(CompletableFuture<?>... cfs) 时，这两种提供超时的方式的行为完全不同!
基本上，似乎 get()做我所期望的(它阻塞当前线程，直到所有 future 都完成)，而 orTimeout()似乎表现得很奇怪(它在第一个 future 完成后尽快解除对当前线程的阻塞)。
下面是一些代码来演示我观察到的行为:

import org.junit.Test;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;

import static java.util.concurrent.TimeUnit.MILLISECONDS;

public class AllOfWithTimeoutTest {

    public static final int TIMEOUT_IN_MILLIS = 100;

    @Test
    public void allOfOrTimeout1() throws InterruptedException, ExecutionException, TimeoutException {
        getAllOfFuture().get(TIMEOUT_IN_MILLIS, MILLISECONDS);
    }

    @Test
    public void allOfOrTimeout2() throws ExecutionException, InterruptedException {
        getAllOfFuture().orTimeout(TIMEOUT_IN_MILLIS, MILLISECONDS);
    }

    private CompletableFuture<Void> getAllOfFuture() {
        return CompletableFuture.allOf(
            CompletableFuture.runAsync(() -> sleep(1)),
            CompletableFuture.runAsync(() -> sleep(2)),
            CompletableFuture.runAsync(() -> sleep(3)),
            CompletableFuture.runAsync(() -> sleep(4)),
            CompletableFuture.runAsync(() -> sleep(5)),
            CompletableFuture.runAsync(() -> sleep(6)),
            CompletableFuture.runAsync(() -> sleep(7)),
            CompletableFuture.runAsync(() -> sleep(8))
        );
    }

    public static void sleep(int millis) {
        try {
            Thread.sleep(millis);
            System.out.format("Had a nap for %s milliseconds.\r\n", millis);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    };
}

allOfOrTimeout1()的打印输出是我所期望的:

Had a nap for 1 milliseconds.
Had a nap for 2 milliseconds.
Had a nap for 3 milliseconds.
Had a nap for 4 milliseconds.
Had a nap for 5 milliseconds.
Had a nap for 6 milliseconds.
Had a nap for 7 milliseconds.
Had a nap for 8 milliseconds.

allOfOrTimeout2()的打印输出不是我所期望的，并且在每次执行时都会略有不同。它通常在前 2 行和 5 行之间打印出来，但从不打印 8 行。这是一个只打印出 2 行的版本:

Had a nap for 1 milliseconds.
Had a nap for 2 milliseconds.

另外，如果我在 IntelliJ 中运行整个测试，最后我会得到一些额外的行:

Had a nap for 1 milliseconds.
Had a nap for 2 milliseconds.
Had a nap for 3 milliseconds.
Had a nap for 4 milliseconds.
Had a nap for 5 milliseconds.
Had a nap for 6 milliseconds.
Had a nap for 7 milliseconds.
Had a nap for 8 milliseconds.



Had a nap for 1 milliseconds.
Had a nap for 2 milliseconds.

Had a nap for 3 milliseconds.
Had a nap for 4 milliseconds.

Process finished with exit code 0
Had a nap for 

我的问题是:

这是 orTimeout() 的预期行为吗？ ?

如果没有，为什么要这样做？

Answer 1

Is this the expected behavior for orTimeout() ?

是的。 OrTimeout是一个非阻塞异步调用，而 get是一个阻塞异步调用。