现在我有一个Account类,包含账户的余额,同时定义了transfer函数实现账户转账
参数为:要转给的账户以及转账的金额
实现为:将当前账户金额减去转账金额,目的账户金额加上转账金额
然后在主函数中创建了两个账户a,b,分别存入1000元;以及两个线程A B,分别实现 a向b转账 和 b向a转账,分别执行10000次
然后开启两个线程,最后打印出两个账户的余额之和,理论上来讲应该是2000元,但是因为存在临界区代码,导致最后之和有时不是2000,但是我手动模拟了很久,还是想不出来为什么会造成这种结果,请问大家可以帮忙解释一下吗?
代码如下:
import java.util.Random;
public class Main {
static Random random = new Random();
public static void main(String[] args) throws InterruptedException {
Account a = new Account(1000);
Account b = new Account(1000);
Runnable runnable1 = () -> {
for(int i = 0;i < 10000;i++){
int temp = getAmount();
a.transfer(b,temp); //a向b转账
System.out.println("a -- > b " + temp + ", a = " + a.getMoney() + "; b = " + b.getMoney() + " sum = " + (a.getMoney() + b.getMoney()));
}
};
Runnable runnable2 = () -> {
for(int i = 0;i < 10000;i++){
int temp = getAmount();
b.transfer(a,temp); //b向a转账
System.out.println("b -- > a " + temp + ", a = " + a.getMoney() + "; b = " + b.getMoney() + " sum = " + (a.getMoney() + b.getMoney()));
}
};
Thread thread1 = new Thread(runnable1);
Thread thread2 = new Thread(runnable2);
thread1.start();
thread2.start();
thread1.join();
thread2.join();
System.out.println("总金额:" + (a.getMoney() + b.getMoney())); //输出总金额
}
public static int getAmount(){
return random.nextInt(98) + 1;
}
}
class Account{
private int money;
public Account(int m){
money = m;
}
public int getMoney(){
return money;
}
public void setMoney(int m){
money = m;
}
public void transfer(Account target,int amount){
if(this.money >= amount){
this.setMoney(this.getMoney() - amount);
target.setMoney(target.getMoney() + amount);
}
}
}