什么是CountDownLatch

今天就跟大家聊聊有关什么是CountDownLatch，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。countDownLatch也是基于AQS,它是AQS共享功能的一个实现
1
countDownLatch构造
public CountDownLatch(int count) {
if (count this.sync = new Sync(count);
}
count最终传递给state ,countDown也是对于state状态的改变private static final class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 4982264981922014374L; Sync(int count) {
setState(count);
} int getCount() {
return getState();
} protected int tryAcquireShared(int acquires) {
return (getState() == 0) ? 1 : -1;
}
}2 countDown实现public void countDown() {
sync.releaseShared(1);
}public final boolean releaseShared(int arg) {
if (tryReleaseShared(a 香港云主机rg)) {
doReleaseShared();
return true;
}
return false;
}
protected boolean tryReleaseShared(int releases) {
// Decrement count; signal when transition to zero
for (;;) {
int c = getState();
if (c == 0)
return false;
int nextc = c-1;
if (compareAndSetState(c, nextc))
return nextc == 0;
}
} private void unparkSuccessor(Node node) {
/*
* If status is negative (i.e., possibly needing signal) try
* to clear in anticipation of signalling. It is OK if this
* fails or if status is changed by waiting thread.
*/
int ws = node.waitStatus;
if (ws compareAndSetWaitStatus(node, ws, 0); /*
* Thread to unpark is held in successor, which is normally
* just the next node. But if cancelled or apparently null,
* traverse backwards from tail to find the actual
* non-cancelled successor.
*/
Node s = node.next;
if (s == null || s.waitStatus > 0) {
s = null;
for (Node t = tail; t != null && t != node; t = t.prev)
if (t.waitStatus s = t;
}
if (s != null)
LockSupport.unpark(s.thread);
}看完上述内容，你们对什么是CountDownLatch有进一步的了解吗？如果还想了解更多知识或者相关内容，请关注开发云行业资讯频道，感谢大家的支持。

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