ABA 问题

加版本号解决 乐观锁

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicStampedReference;

/**

 * @description 描述
 *  AtomicReference 原子引用
 *  AtomicStampedReference 加了时间戳  类似于乐观锁！ 通过版本号
 */
public class CasAbaAtomicStampedReference {

    public static void main(String[] args) throws InterruptedException {
        AtomicStampedReference atomicStampedReference = new AtomicStampedReference<>(5, 1);

        /**
         *  @description:A线程已经将5修改为其他数
         *  @author yangxj
         *  @date 2020/2/25 17:23
         */
        new Thread(() -> {
            //获得版本号
            System.out.println("A stamp 01=>"+atomicStampedReference.getStamp());

            atomicStampedReference.compareAndSet(5,200,atomicStampedReference.getStamp(),atomicStampedReference.getStamp() + 1);
        },"A").start();


        /**
         *  @description:C线程是小偷，偷偷的改动数据，然后又改回原来的5
         *  @author yangxj
         *  @date 2020/2/25 17:23
         */
        new Thread(() -> {
            // 保证上面的线程先执行完毕！
            try {
                TimeUnit.SECONDS.sleep(3);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            //获得版本号
            System.out.println("C stamp 01=>"+atomicStampedReference.getStamp());

            atomicStampedReference.compareAndSet(200,210,atomicStampedReference.getStamp(),atomicStampedReference.getStamp() + 1);
            System.out.println("C stamp 02=>"+atomicStampedReference.getStamp());
            atomicStampedReference.compareAndSet(210,5,atomicStampedReference.getStamp(),atomicStampedReference.getStamp() + 1);
            System.out.println("C stamp 03=>"+atomicStampedReference.getStamp());
        },"C").start();

      
        new Thread(() -> {

            // 保证上面的线程先执行完毕！
            try {
                TimeUnit.SECONDS.sleep(7);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            //获得版本号
            System.out.println("B stamp 01=>"+atomicStampedReference.getStamp());

            boolean isSuccess = atomicStampedReference.compareAndSet(5, 1024, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1);
            System.out.println("线程B执行成功了吗？" + isSuccess);
            System.out.println("B 最新的stamp："+atomicStampedReference.getStamp());
            System.out.println("B 当前的最新值："+atomicStampedReference.getReference());
        },"B").start();
    }
}

AtomicStampedReference atomicStampedReference = new AtomicStampedReference<>(5, 1);
System.out.println(atomicStampedReference.getStamp());
atomicStampedReference.compareAndSet(5  , 100 , atomicStampedReference.getStamp() ,1);

System.out.println(atomicStampedReference.getStamp());