原 java 自旋锁

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自旋锁（spinlock）：

是指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，这样的好处是减少线程上下文切换的消耗，缺点是循环会消耗CPU。

手写一个自旋锁的代码如下：

package com.mszl.thread;

import java.util.concurrent.atomic.AtomicReference;

/**
 * 功能：手写一个自旋锁
 * 备注：更多资料请访问 http://www.91mszl.com
 * @author bobo teacher
 */
public class SpinLockDemo {
	
	AtomicReference<Integer> rf=new AtomicReference<Integer>(10);
	
	public void myLock(){
		Thread t=Thread.currentThread();
		System.out.println(t.getName() + " myLock ");
		while(!rf.compareAndSet(10, 80)){
			
		}
	}
	
	public void myUnLock(){
		Thread t=Thread.currentThread();
		boolean flag=rf.compareAndSet(80, 10);
		System.out.println(t.getName() + " myUnLock ");
	}
	
	public static void main(String[] args) {
		SpinLockDemo sk=new SpinLockDemo();
		
		Thread t1=new Thread(new Runnable() {
			@Override
			public void run() {
				sk.myLock();
				try {
					Thread.sleep(3000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				sk.myUnLock();
			}
		});
		t1.start();
		
		try {
			Thread.sleep(5000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		
		Thread t2=new Thread(new Runnable() {
			@Override
			public void run() {
				sk.myLock();
				
				sk.myUnLock();
			}
		});
		t2.start();
	}
	

}

执行结果：

Thread-0 myLock 
Thread-0 myUnLock 
Thread-1 myLock 
Thread-1 myUnLock