Java利用AQS实现自定义锁

   
    private volatile int state;

    
    protected final int getState() {
        return state;
    }
 
    
    protected final void setState(int newState) {
        state = newState;
    }
    
    protected final boolean compareAndSetState(int expect, int update) {
        // See below for intrinsics setup to support this
        return unsafe.compareAndSwapint(this, stateOffset, expect, update);
    }

//自定义锁（不可重入）（独占锁）（条件变量）
class MyLock implements Lock{
    //内部类，AQS同步器类
    class MySync extends AbstractQueuedSynchronizer{
        @Override
        protected boolean tryAcquire(int arg) {
            if (compareAndSetState(0,1)){
                System.out.println("获得锁成功");
                //加上了锁,并设置owner为当前线程
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            System.out.println("获得锁失败");
            return false;
        }
 
        @Override
        protected boolean tryRelease(int arg) {
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }
 
        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }
 
        public Condition newCondition(){
            return new ConditionObject();
        }
    }
 
    private MySync mySync = new MySync();
 
    @Override //加锁（不成功进入阻塞队列等待）
    public void lock() {
        mySync.acquire(1);
    }
 
    @Override //加锁可打断
    public void lockInterruptibly() throws InterruptedException {
        mySync.acquireInterruptibly(1);
    }
 
    @Override //加锁(不成功不会进入阻塞队列等待，可以去做其他事情)
    public boolean tryLock() {
        return mySync.tryAcquire(1);
    }
 
    @Override //尝试加锁 带时间
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return mySync.tryAcquireNanos(1,unit.toNanos(time));
    }
 
    @Override //释放锁
    public void unlock() {
        mySync.release(1);
    }
 
    @Override //创建条件变量
    public Condition newCondition() {
        return mySync.newCondition();
    }
}