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ABADemo.java
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53 lines (45 loc) · 2.74 KB
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/**
* @program JavaBooks
* @description: ABADemo，ABA问题的小例子
* @author: mf
* @create: 2020/02/14 00:17
*/
package com.juc.cas;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicStampedReference;
public class ABADemo {
static AtomicInteger atomicInteger = new AtomicInteger(100);
static AtomicStampedReference<Integer> atomicStampedReference = new AtomicStampedReference<>(100, 1);
public static void main(String[] args) {
System.out.println("=====ABA的问题产生=====");
new Thread(() -> {
atomicInteger.compareAndSet(100, 101);
atomicInteger.compareAndSet(101, 100);
}, "t1").start();
new Thread(() -> {
// 保证线程1完成一次ABA问题
try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); }
System.out.println(atomicInteger.compareAndSet(100, 2020) + " " + atomicInteger.get());
}, "t2").start();
try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); }
System.out.println("=====解决ABA的问题=====");
new Thread(() -> {
int stamp = atomicStampedReference.getStamp(); // 第一次获取版本号
System.out.println(Thread.currentThread().getName() + " 第1次版本号" + stamp);
try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); }
atomicStampedReference.compareAndSet(100, 101, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1);
System.out.println(Thread.currentThread().getName() + "\t第2次版本号" + atomicStampedReference.getStamp());
atomicStampedReference.compareAndSet(101, 100, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1);
System.out.println(Thread.currentThread().getName() + "\t第3次版本号" + atomicStampedReference.getStamp());
}, "t3").start();
new Thread(() -> {
int stamp = atomicStampedReference.getStamp();
System.out.println(Thread.currentThread().getName() + "\t第1次版本号" + stamp);
try { TimeUnit.SECONDS.sleep(4); } catch (InterruptedException e) { e.printStackTrace(); }
boolean result = atomicStampedReference.compareAndSet(100, 2020, stamp, stamp + 1);
System.out.println(Thread.currentThread().getName() + "\t修改是否成功" + result + "\t当前最新实际版本号：" + atomicStampedReference.getStamp());
System.out.println(Thread.currentThread().getName() + "\t当前最新实际值：" + atomicStampedReference.getReference());
}, "t4").start();
}
}