java:等到另一个线程执行一条语句n次

Question

停止线程并等待语句(或方法)被另一个线程执行一定次数的最佳方法是什么？ 我在想这样的事情(让“数字”成为一个整数):

number = 5;
while (number > 0) {
   synchronized(number) { number.wait(); }
}

...

synchronized(number) {
   number--;
   number.notify();
}

显然这行不通，首先是因为您似乎不能在 int 类型上使用 wait()。此外，对于这样一个简单的任务，我想到的所有其他解决方案都非常复杂。有什么建议么？ (谢谢!)

Answer 1

听起来您正在寻找 CountDownLatch .

CountDownLatch latch = new CountDownLatch(5);
...
latch.await(); // Possibly put timeout


// Other thread... in a loop
latch.countDown(); // When this has executed 5 times, first thread will unblock

A Semaphore也可以:

Semaphore semaphore = new Semaphore(0);
...
semaphore.acquire(5);

// Other thread... in a loop
semaphore.release(); // When this has executed 5 times, first thread will unblock