Java死锁示例

青旅半醒 2023-09-29 17:42 5阅读 0赞

#### 文章目录 ####

*  Java死锁
 *   *  1.1 形成死锁的四个必要条件
     *  1.2 示例

## Java死锁 ##

### 1.1 形成死锁的四个必要条件 ###

*  互斥条件：一份资源不能同时被多个线程使用
 *  请求与保持：占有一份资源，同时申请其他的资源
 *  不剥夺条件：占有的资源不能被强行剥夺
 *  循环等待：形成一种头尾相接的等待资源关系

### 1.2 示例 ###

这里以化妆为例：同时获得口红和镜子才能开始化妆  
  
**DeadLock.java**  
  
`这里两个人同时开始化妆，g1先拿到了口红，g2先拿到了镜子。然后g1在等待镜子，同时也不会让出口红；g2在等待口红，同时也不会让出镜子。形成死锁`

package com.peng.sync;
    
    public class DeadLock{
        
        public static void main(String[] args) {
        
            Makeup g1 = new Makeup(0, "美羊羊");
            Makeup g2 = new Makeup(1, "红太狼");
            g1.start();
            g2.start();
        }
    }
    
    class Lipstick{
        
    
    }
    
    class Mirror{
        
    
    }
    
    class Makeup extends Thread{
        
        static Lipstick lipstick = new Lipstick();
        static Mirror mirror = new Mirror();
        int choice;
        String girlName;
        public Makeup(int choice, String girlName){
        
            this.choice = choice;
            this.girlName = girlName;
        }
        @Override
        public void run() {
        
            // 化妆
            try {
        
                makeup();
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
        }
    
        private void makeup() throws InterruptedException{
        
            if (choice == 0){
        
                synchronized(lipstick){
        
                    System.out.println(girlName + "拿到了口红");
                    Thread.sleep(1000);
                    synchronized(mirror){
        
                        System.out.println(girlName+ "拿到了镜子");
                    }
                }
                System.out.println(girlName + " start to makeup");
            }
            else{
        
                synchronized(mirror){
        
                    System.out.println(girlName + "拿到了镜子");
                    Thread.sleep(2000);
                    synchronized(lipstick){
        
                        System.out.println(girlName + "拿到了口红");
                    }
                }
                System.out.println(girlName + " start to makeup");
            }
        }
    }