Java多线程不安全代码示例

Dear 丶 2023-09-29 17:40 67阅读 0赞

#### 文章目录 ####

*  线程不安全代码示例
 *  一、抢票
 *  二、银行取钱

## 线程不安全代码示例 ##

*  当出现多个线程操作同一个对象的时候，如果不加以控制，则会出现错误的情况。
 *  这里举两个例子，一个是抢票，一个是取钱。

## 一、抢票 ##

**UnsafeBuyTicket.java**

> 多个人抢票，出现两个人抢到了同一张票的情况

package com.peng.sync;
    
    public class UnsafeBuyTicket{
        
        public static void main(String[] args) {
        
    
            BuyTicket ticket = new BuyTicket(10);
            new Thread(ticket,"小明").start();
            new Thread(ticket, "老师").start();
            new Thread(ticket, "黄牛").start();
        }
    }
    
    class BuyTicket implements Runnable{
        
        private int ticketNum;
        private boolean flag = true;
    
        public BuyTicket(int ticketNum){
        
            this.ticketNum = ticketNum;
        }
        @Override
        public void run() {
        
            while (flag){
        
                buy();
                try {
        
                    Thread.sleep(200);
                } catch (InterruptedException e) {
        
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    
        private void buy(){
        
            if (ticketNum <= 0){
        
                flag = false;
                return;
            }
            else{
        
                System.out.println(Thread.currentThread().getName() + "抢到了票" + ticketNum--);
            }
        }
    }

## 二、银行取钱 ##

**UnsafeBank.java**

> 两个人同时从一个账户中取钱，账户余额变为负数

package com.peng.sync;
    
    public class UnsafeBank {
        
        public static void main(String[] args) {
        
            Account abc = new Account("abc", 10000);
            Drawing handsome = new Drawing(abc, 5000);
            Drawing girlfriend = new Drawing(abc, 7000);
            new Thread(handsome,"大帅哥").start();
            new Thread(girlfriend, "女朋友").start();
        }
        
    }
    
    class Account{
        
        String accountName;
        int money;
        public Account(String accountName, int money){
        
            this.accountName = accountName;
            this.money = money;
        }
    }
    
    class Drawing implements Runnable{
        
        Account account;
        int drawedMoney;
        public Drawing(Account a, int d){
        
            account = a;
            drawedMoney = d;
        }
    
        @Override
        public void run() {
        
            if (account.money - drawedMoney <= 0){
        
                System.out.println("账户余额不足了");
                return;
            }
            try {
        
                Thread.sleep(3000);
            } catch (InterruptedException e) {
        
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            account.money = account.money - drawedMoney;
            System.out.println(Thread.currentThread().getName() + "取了" + drawedMoney + "钱");
            System.out.println("账户余额为:" + account.money);
        }
        
    }