Bank类
public class Bank {
static int money = 1000;
Object lock = "a";
public void ATM(int money) {
synchronized(lock)
{
if(money == 100)
{
Bank.money -= money;
System.out.println("A取走100，剩余" + Bank.money);
}
if(money == 200)
{
Bank.money -= money;
System.out.println("B取走200，剩余" + Bank.money);
}
}
}
}
PersonA类
public class PersonA extends Thread {
Bank bank;
public PersonA(Bank bank) {
this.bank = bank;
}
@Override
public void run() {
while (bank.money >= 100) {
bank.ATM(100);
}
}
}
PersonB类
public class PersonB extends Thread{
Bank bank;
public PersonB(Bank bank) {
this.bank = bank;
}
@Override
public void run() {
while(bank.money >= 200) {
bank.ATM(200);
}
}
}
测试类
public class Demo {
public static void main(String[] args) {
Bank bank = new Bank();
Thread a = new PersonA(bank);
Thread b = new PersonB(bank);
a.start();
b.start();
}
}
输出结果：
B取走200，剩余800
B取走200，剩余600
B取走200，剩余400
B取走200，剩余200
B取走200，剩余0
A取走100，剩余-100
为什么最后Bank中money都为0了，A还会在取走一次钱？？

你的同步synchronized这个关键词并没有什么用，因为判断都是在外面做的，相当于脏数据了。改下ATM方法
public void ATM(int money) {
synchronized (lock) {
if (money == 100) {
if(Bank.money >= 100){
Bank.money -= money;
System.out.println("A取走100，剩余" + Bank.money);
}
}
if (money == 200) {
if(Bank.money >= 200){
Bank.money -= money;
System.out.println("B取走200，剩余" + Bank.money);
}
}
}
}

亲，你是自学吗？

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