package com.dayu.inter;import sun.rmi.runtime.NewThreadAction;import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicStampedReference;/*** @Author: dayu* @Date: 2019/9/24 15:13* @Description*/
public class ABADemo {public static void main(String[] args) {System.out.println("=========下面是ABA问题的产生==========");AtomicReference<Integer> atomicReference = new AtomicReference<>(100);new Thread(() -> {System.out.println(atomicReference.compareAndSet(100, 101)+"\t"+atomicReference.get());System.out.println(atomicReference.compareAndSet(101, 100)+"\t"+atomicReference.get());}, "t1").start();new Thread(() -> {//休息一会，让线程t1先执行一遍ABA的问题try {TimeUnit.SECONDS.sleep(1);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(atomicReference.compareAndSet(100, 2000)+"\t"+atomicReference.get());}, "t2").start();//休息一会,确保上面两个线程执行完毕try {TimeUnit.SECONDS.sleep(2);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("=========下面是ABA问题的解决==========");//有点类似于乐观锁//初始值设定100，时间戳（版本号=1）AtomicStampedReference<Integer> atomicStampedReference = new AtomicStampedReference<>(100, 1);new Thread(() -> {int stamp = atomicStampedReference.getStamp();System.out.println(Thread.currentThread().getName()+"\t 第一次获取版本号"+stamp);//休息一会,等待t4获取版本号try {TimeUnit.SECONDS.sleep(1);} catch (InterruptedException e) {e.printStackTrace();}atomicStampedReference.compareAndSet(100,101,atomicStampedReference.getStamp(),atomicStampedReference.getStamp()+1);System.out.println(Thread.currentThread().getName()+"\t 第2次获取版本号"+atomicStampedReference.getStamp());atomicStampedReference.compareAndSet(101,100,atomicStampedReference.getStamp(),atomicStampedReference.getStamp()+1);System.out.println(Thread.currentThread().getName()+"\t 第3次获取版本号"+atomicStampedReference.getStamp());}, "t3").start();//t4和t3最初获取到的版本号一致，new Thread(() -> {int stamp = atomicStampedReference.getStamp();System.out.println(Thread.currentThread().getName()+"\t 第一次获取版本号"+stamp);//休息一会,确保t3完成一次ABAtry {TimeUnit.SECONDS.sleep(4);} catch (InterruptedException e) {e.printStackTrace();}boolean result = atomicStampedReference.compareAndSet(100, 2019, stamp, stamp + 1);System.out.println(Thread.currentThread().getName()+"\t 是否修改成功："+result+"\t 当前真实的版本号："+atomicStampedReference.getStamp()+"\t 当前真实的值："+atomicStampedReference.getReference());}, "t4").start();}
}