//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

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);

    }

}

abstract static class Sync extends AbstractQueuedSynchronizer 

static final class NonfairSync extends Sync