java自旋锁

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此文章不涉及与互斥锁等比比较，只是单纯的介绍一个自旋锁，如果想要了解更多可以点击参考链接

一个自旋锁例子

自旋锁的介绍原理等过程我就不在此介绍了，下面的参考已经写的非常不错了！

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/***
 * 自旋锁
 * @author Joker
 *
 */
public class SpinLock {
	
	AtomicReference<Thread> owner = new AtomicReference<Thread>();
	private int count ;
	
	public void lock() {
		Thread currentThread = Thread.currentThread();
		System.out.println("lock() -> " + currentThread.getName());
		if (currentThread == owner.get()) {
			count++; // 获取锁的次数
			return ;
		}
		
		// 当线程越来越多由于while循环会浪费cpu时间片，compareAndSet需要多次对同一内存进行访问
		while (!owner.compareAndSet(null, currentThread)) {
			
		}
	}
	
	public void unLock() {
		Thread currentThread = Thread.currentThread();
		System.out.println("unLock() -> " + currentThread.getName());
		if (currentThread == owner.get()) {
			if (count > 0) {
				count--;
			} else {
				owner.compareAndSet(currentThread, null);
			}
		}
	}
}
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public class SpinLockTest implements Runnable{
	static int sum ;
	private SpinLock lock;
	
	
	public SpinLockTest(SpinLock lock) {
		this.lock = lock;
	}
	
	public void run() {
		this.lock.lock();
		this.lock.lock();
		System.out.println("当前线程 " + Thread.currentThread().getName() + " start...");
		sum++;
		System.out.println("当前线程 " + Thread.currentThread().getName() + " end...");
		
		this.lock.unLock();
		this.lock.unLock();
	}
	
	public static void main(String[] args) throws InterruptedException {
		SpinLock lock = new SpinLock();
		for (int i = 1; i < 5; i++) {
			SpinLockTest lockTest = new SpinLockTest(lock);
			Thread t = new Thread(lockTest, "thread-lock-"+i);
			t.start();
		}
		
		Thread.sleep(1000);
		System.out.println(sum);
	}
}

最后附上一张我自己画的一张运行图

java自旋锁

参考

http://www.cnblogs.com/cposture/p/SpinLock.html#_label0

人生苦短，我要打赏!