自旋锁入门

自旋锁Demo

public class Spinlock {
    AtomicReference serialNumber = new AtomicReference();
    public void LockMe() {
        Thread thread = Thread.currentThread();
        System.out.println(thread.getName() + "加锁");
        while (!serialNumber.compareAndSet(null, thread)) {
        }
    }
    public void unLockMe() {
        Thread thread = Thread.currentThread();
        System.out.println(thread.getName() + "解锁");
        serialNumber.compareAndSet(thread, null);
    }
}

  public static void main(String[] args) throws Exception {
        Spinlock spinlock = new Spinlock();
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    spinlock.LockMe();
                    TimeUnit.SECONDS.sleep(5);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    spinlock.unLockMe();
                }
            }
        }, "A").start();
        TimeUnit.SECONDS.sleep(1);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    spinlock.LockMe();
                } finally {
                    spinlock.unLockMe();
                }
            }
        }, "B").start();
    }
A加锁
B加锁 //等待一段时间
A解锁
B解锁  
尝试获取锁的线程不会立即阻塞，而是采用循环的方式去尝试获取锁。
目的:减少线程上下文频繁的切换而引起的性能损耗，所以才自旋让当前线程一直占用资源。
好处:循环比较获取直到成功为止，没有类似wait()的阻塞。
缺点: 是循环会消耗CPU资源

本文地址：https://blog.csdn.net/qq_40721300/article/details/110230992