AQS是一个同步器的基础类，里面的关键字段：
//如下关键字段都是volatile类型
/**
* Head of the wait queue, lazily initialized. Except for
* initialization, it is modified only via method setHead. Note:
* If head exists, its waitStatus is guaranteed not to be
* CANCELLED.
*/
private transient volatile Node head; //获取锁的链式队列的头
/**
* Tail of the wait queue, lazily initialized. Modified only via
* method enq to add new wait node.
*/
private transient volatile Node tail;//获取锁的链式队列的尾
/**
* The synchronization state.
*/
private volatile int state; //记录所的状态
通过如下示例代码进行跟踪查看队列实际细节：
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock; public class AQS {
public static void main(String[] args) throws Exception { final Lock lock = new ReentrantLock(); lock.lock();
lock.lock();
newThread(lock,"lock-1").start();
Thread.sleep(500);
newThread(lock,"lock-2").start();
Thread.sleep(500);
newThread(lock,"lock-3").start();
Thread.sleep(500);
//断点处，可以在此处进行跟踪
lock.lock(); Thread.sleep(5000000);
lock.unlock();
lock.unlock();
lock.unlock(); } public static Thread newThread(final Lock lock,final String threadName ) {
return new Thread(new Runnable() { @Override
public void run() {
System.out.println(threadName+"正在获取锁！");
lock.lock();
}
},threadName); } }
注意类的继承细节：
abstract static class Sync extends AbstractQueuedSynchronizer
static final class NonfairSync extends Sync
此时细节：
三个线程lock-1，lock-2，lock-3正在队列中等待获取锁。
接下来查看一下lock-1如何存储到等待队列中的：