java之AQS(AbstractQueuedSynchronizer)用法解读

import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.LockSupport;

// 自定义锁类
class MyLock implements Lock {
    // 静态内部类，继承AQS
    private static class Sync extends AbstractQueuedSynchronizer {
        // 是否处于独占模式
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        // 尝试获取锁，当状态为0时获取锁成功
        public boolean tryAcquire(int acquires) {
            assert acquires == 1; // 只允许获取1个单位的锁
            if (compareAndSetState(0, 1)) {
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        // 尝试释放锁，将状态设置为0
        protected boolean tryRelease(int releases) {
            assert releases == 1; // 只允许释放1个单位的锁
            if (getState() == 0) throw new IllegalMonitorStateException();
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

        // 提供条件变量
        Condition newCondition() { return new ConditionObject(); }
    }

    // 将操作代理到Sync上
    private final Sync sync = new Sync();

    // 实现Lock接口的方法
    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.release(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }

    public static void main(String[] args) {
        MyLock lock = new MyLock();

        Runnable task = () -> {
            lock.lock();
            try {
                System.out.println(Thread.currentThread().getName() + " 获取锁");
                // 模拟任务执行
                LockSupport.parkNanos(TimeUnit.SECONDS.toNanos(1));
            } finally {
                System.out.println(Thread.currentThread().getName() + " 释放锁");
                lock.unlock();
            }
        };

        Thread t1 = new Thread(task, "Thread-1");
        Thread t2 = new Thread(task, "Thread-2");

        t1.start();
        t2.start();
    }
}