【并发编程】AQS学习

package net.jcip.examples;
import java.util.concurrent.locks.*;
import net.jcip.annotations.*;
/**
 * OneShotLatch
 * <p/>
 * Binary latch using AbstractQueuedSynchronizer
 *
 * @author Brian Goetz and Tim Peierls
 */
@ThreadSafe
public class OneShotLatch {
    private final Sync sync = new Sync(); //基于委托的方式
    public void signal() {
        sync.releaseShared(0);  ////会调用 tryAcquireShared
    }
    public void await() throws InterruptedException {
        sync.acquireSharedInterruptibly(0);  //会调用 tryAcquireShared
    }
    private class Sync extends AbstractQueuedSynchronizer {  //内部私有类
        protected int tryAcquireShared(int ignored) {
            // Succeed if latch is open (state == 1), else fail
            return (getState() == 1) ? 1 : -1;
        }
        protected boolean tryReleaseShared(int ignored) {
            setState(1); // Latch is now open
            return true; // Other threads may now be able to acquire
        }
    }
}