多线程，拜大神，锁

[90后北京程序员]

public class Demo{
	public static int rocket = 20;
	public static void main(String[] args){
		MyThread mt1 = new MyThread();
		Thread t1 = new Thread(mt1);
		MyThread2 t2 = new MyThread2();
		t1.start();
		t2.start();
	}
}
class MyThread implements Runnable{
	public  void run(){
	synchronized("11"){
		while(Demo.rocket>0){
		 
			if(Demo.rocket==1){
				try{
					Thread.sleep(1000);
				}catch(Exception e){
					e.printStackTrace();
				}
			}
			Demo.rocket--;
			System.out.println("1111卖票，剩余:"+Demo.rocket+"张票");
		}
	}
	}
}
class MyThread2 extends Thread{
	public   void run(){
	synchronized("11111"){
		while(Demo.rocket>0){ 
		 
			Demo.rocket--;
			System.out.println("22222222卖票，剩余 :"+Demo.rocket+"张票........");
		}
	}
	}
}
 

结果：
1111卖票，剩余:19张票
22222222卖票，剩余 :18张票.....
1111卖票，剩余:17张票
22222222卖票，剩余 :16张票.....
1111卖票，剩余:15张票
1111卖票，剩余:13张票
22222222卖票，剩余 :14张票.....
1111卖票，剩余:12张票
22222222卖票，剩余 :11张票.....
22222222卖票，剩余 :9张票......
22222222卖票，剩余 :8张票......
1111卖票，剩余:10张票
1111卖票，剩余:6张票
1111卖票，剩余:5张票
22222222卖票，剩余 :7张票......
22222222卖票，剩余 :3张票......
1111卖票，剩余:4张票
1111卖票，剩余:1张票
22222222卖票，剩余 :2张票......
22222222卖票，剩余 :0张票......
1111卖票，剩余:-1张票
为啥结果还有-1啊？怎样解决？

[爱跳舞的铅笔头]

有-1是线程同步现象导致的，判断while条件的时候肯定是满足的，进去执行的时候，另一个线程将Demo.rocket执行的结果为0.所以……

[蟑螂-roach]

你锁rocket变量，其他线程不就进不去了吗，或者你锁Demo类也行的。你还是看看线程同步吧

[seqwait]

要锁住demo这个对象

package com.xiehou.th;

public class Demo {
	
	public static int rocket = 20;

	public static void main(String[] args) {
		
		Demo demo=new Demo();
		
		MyThread mt1 = new MyThread(demo);
		Thread t1 = new Thread(mt1);
		MyThread2 t2 = new MyThread2(demo);
		t1.start();
		t2.start();
	}
}

class MyThread implements Runnable {
	
	public Demo demo;
	
	public MyThread(Demo demo){
		this.demo=demo;
	}
	
	public void run() {
		synchronized (demo) {
			while (Demo.rocket > 0) {

				if (Demo.rocket == 1) {
					try {
						Thread.sleep(1000);
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
				Demo.rocket--;
				System.out.println("[1111]卖第:" + Demo.rocket + "张票");
			}
		}
	}
}

class MyThread2 extends Thread {
	
   public Demo demo;
	
	public MyThread2(Demo demo){
		this.demo=demo;
	}
	
	public void run() {
		synchronized (demo) {
			while (Demo.rocket > 0) {

				Demo.rocket--;
				System.out.println("[2222]第 :" + Demo.rocket + "张票");
			}
		}
	}
}

[非凡90]

synchronized(this)，就ok了！

[非凡90]

public class Demo{ public static int rocket = 20; public static void main(String[] args){ MyThread mt1 = new MyThread(); Thread t1 = new Thread(mt1); MyThread2 t2 = new MyThread2(); t1.start(); t2.start(); } } class MyThread implements Runnable{ public void run(){ synchronized(this){ while(Demo.rocket>0){ if(Demo.rocket==1){ try{ Thread.sleep(1000); }catch(Exception e){ e.printStackTrace(); } } Demo.rocket--; System.out.println("1111卖票，剩余:"+Demo.rocket+"张票"); } } } } class MyThread2 extends Thread{ public void run(){ synchronized(this){ while(Demo.rocket>0){ Demo.rocket--; System.out.println("22222222卖票，剩余 :"+Demo.rocket+"张票........"); } } } }

[ntwarren]

你两个锁不是同一个锁，不起作用的，要锁同一个对象才行的。

[90后北京程序员]

谢谢以上回答