Question

有人可以用简单的方式解释CompletableFuture的原始来源吗？特别是在timedGet（long nanos）中会发生什么？这是源代码链接https://github.com/frohoff/jdk8u-jdk/blob/master/src/share/classes/java/util/concurrent/CompletableFuture.java

CompletableFuture如何监视线程的执行并超时？

Answer 1

我不会自己解释整个CompletableFuture，因为它大约有2K行，但是我绝对会解释timedGet()

请注意，我们在这里讨论的是OpenJDK，OracleJDK有点不同。

在肉部分之前进行一些检查，之后进行一些清理。我要离开他们。

long d = System.nanoTime() + nanos;
// Arguments are interruptible, nanos, deadline
Signaller q = new Signaller(true, nanos, d == 0L ? 1L : d); // avoid 0
boolean queued = false;

// We wait until we get the result
// If it's already there, we simply return it
while ((r = result) == null) {
    // So, the result is not there
    // If it's the first time we run this loop, or we didn't manage to push signaller on the stacked queued=false 
    if (!queued)
         queued = tryPushStack(q);
    // Something interrupted us. It could be either thread interrupt or timeout
    else if (q.interruptControl < 0 || q.nanos <= 0L) {
        q.thread = null;
        cleanStack();
        if (q.interruptControl < 0)
            return null;
        throw new TimeoutException();
    }
    else if (q.thread != null && result == null) {
       try {
          // Waits for q, without blocking the thread
          ForkJoinPool.managedBlock(q);
       } catch (InterruptedException ie) {
           q.interruptControl = -1;
       }
   }
}

CompletableFuture简化的自定义示例

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