java锁经典示例——卖车票场景

场景：20张车票 3个窗口同时售票

1.不加锁

package com.yao.lock;

/**
 * 不加锁的情况
 */
public class Runnable_demo implements Runnable{
    private int ticket=20;
    public Runnable_demo(){
    }
    public void run() {
        for(int i=0;i<20;i++){
                if(this.ticket>0){
                    //休眠1s秒中，为了使效果更明显，否则可能出不了效果
                    try {
                        Thread.sleep(1000);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName()+"号窗口卖出："+this.ticket--+"号票");
                }
        }
    }  

     public static void main(String args[]){
         Runnable_demo demo=new Runnable_demo();
         //基于火车票创建三个窗口
         new Thread(demo,"a").start();
         new Thread(demo,"b").start();
         new Thread(demo,"c").start();
     }  

} 

运行结果：

2.synchronized

package com.yao.lock;

public class Runnable_demo1 implements Runnable{
    private int ticket=20;
    private boolean isSoldOut = false;
    public Runnable_demo1(){
    }
    public void run() {
        for(int i=0;i<20;i++){
            synchronized(this){
                if(this.ticket>0){
                    //休眠1s秒中，为了使效果更明显，否则可能出不了效果
                    try {
                        Thread.sleep(1000);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName()+"号窗口卖出："+this.ticket--+"号票");
                }else{
                    if(!isSoldOut){
                        System.out.println("售罄");
                        isSoldOut = true;
                    }
                }
            }  

        }
    }  

     public static void main(String args[]){
         Runnable_demo1 demo=new Runnable_demo1();
         //基于火车票创建三个窗口
         new Thread(demo,"a").start();
         new Thread(demo,"b").start();
         new Thread(demo,"c").start();
     }
}

运行结果：

3.Lock

package com.yao.lock;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Runnable_demo2 {
      public static void main(String[] args) {
        // 创建3个线程对象
        SellTicket st = new SellTicket();

        Thread t1 = new Thread(st, "窗口1");
        Thread t2 = new Thread(st, "窗口2");
        Thread t3 = new Thread(st, "窗口3");

        // 启动线程
        t1.start();
        t2.start();
        t3.start();
      }
    }

    class SellTicket implements Runnable {
      private int ticket = 20;
      private Lock lock = new ReentrantLock();

      public void run() {
        while (true) {
          lock.lock();

          if (ticket > 0) {
            try {
              Thread.sleep(1000);
            } catch (InterruptedException e) {
              e.printStackTrace();
            }

            System.out.println(Thread.currentThread().getName() + "正在出售第" + (ticket--) + "张票。");
          }
          lock.unlock();
        }
      }
    }

运行结果：