int current = unsafe.getIntVolatile(this,valueOffset);
if (unsafe.compareAndSwapInt(this,valueOffset,current,current+2)){
break;
}
}
System.out.println("非法组织洗钱，加入2元，余额："+k);
}
public void oldSystemTransfer() throws InterruptedException {
ABATest abaTest = new ABATest();
System.out.println("账户余额："+k);
new Thread(new Runnable() {
@Override
public void run() {
try {
abaTest.transferOld();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
Thread.sleep(20);
abaTest.cleanMoneyAdd();
Thread.sleep(20);
abaTest.cleanMoneySub();
Thread.sleep(200);
System.out.println("银行卡原来余额为10，接收转账1元，故期望余额为11元。实际余额："+abaTest.k);
}
public static void main(String[] args) throws InterruptedException {
ABATest abaTest = new ABATest();
abaTest.oldSystemTransfer();
/**
* 运行结果：
* 账户余额：10
* 开始转账（旧系统：存在ABA问题）
* 由于CPU抢占问题，转账程序阻塞100ms（为了将可能出现的ABA问题，变成肯定出现）
* 非法组织洗钱，加入2元，余额：12
* 非法组织洗钱，盗走2元，余额：10
* 银行转账1元，成功。余额：11
* 银行卡原来余额为10，接收转账1元，故期望余额为11元。实际余额：11
*/
}
}
ABAResolveTest
这是一个修复了ABA问题的示例。示例中银行正常发现客户账户上的非法洗钱行为。
package tech.jarry.learning.netease.casWithABA;
import java.util.concurrent.atomic.AtomicStampedReference;
/**
* @Description：
* @Author: jarry
*/
public class ABAResolveTest {
private AtomicStampedReference<Integer> kReference = new AtomicStampedReference<>(10,0);
private void transferNew() throws InterruptedException {
System.out.println("开始转账（新系统：解决了ABA问题）");
while(true) {
Integer currentReference = kReference.getReference();
int stamp = kReference.getStamp();
System.out.println("由于CPU抢占问题，转账程序阻塞100ms");
Thread.sleep(100);
if (kReference.compareAndSet(currentReference,currentReference+1,stamp,stamp+1)){
System.out.println("银行转账"+1+"元，成功。余额："+kReference.getReference());
break;
}
System.err.println("警告：账户存在交易记录以外的资金流动");
}
}
private void cleanMoneySub(){
int stamp = kReference.getStamp();
kReference.set(kReference.getReference()+2,stamp+1);
System.out.println("非法组织洗钱，盗走2元，余额："+kReference.getStamp());
}
private void cleanMoneyAdd(){
int stamp = kReference.getStamp();
kReference.set(kReference.getReference()-2,stamp+1);
System.out.println("非法组织洗钱，加入2元，余额："+kReference.getStamp());
}
private void newSystemTransfer() throws InterruptedException {
ABAResolveTest abaResolveTest = new ABAResolveTest();
System.out.println("账户余额："+abaResolveTest.kReference.getReference());
new Thread(new Runnable() {
@Override
public void run() {
try {
abaResolveTest.transferNew();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
Thread.sleep(20);
abaResolveTest.cleanMoneyAdd();
Thread.sleep(20);
abaResolveTest.cleanMoneySub();
Thread.sleep(200);
System.out.println("银行卡原来余额为10，接收转账1元，故期望余额为11元。实际余额："+abaResolveTest.kReference.getReference());
}
public static void main(String[] args) throws InterruptedException {
ABAResolveTest abaResolveTest = new ABAResolveTest();
abaResolveTest.newSystemTransfer();
/**
* 运行结果：
* 账户余额：10
* 开始转账（新系统：解决了ABA问题）
* 由于CPU抢占问题，转账程序阻塞100ms
* 非法组织洗钱，加入2元，余额：1
* 非法组织洗钱，盗走2元，余额：2
* 警告：账户存在交易记录以外的资金流动