线程初学

package Tread;

class PP implements Runnable{
public int tickets=200;
String str=new String("123");
public void run(){
while(true){
synchronized(this.str){

if(tickets>0){
System.out.println(Thread.currentThread().getName()+"卖出去的票数是:"+tickets--);
}
else
{
break;
}
}
}
}
}
public class Threade_14 {
public static void main(String[] args) {
PP pp =new PP();
Thread tt1=new Thread(pp);
Thread tt2=new Thread(pp);
Thread tt3=new Thread(pp);
tt1.start();
tt2.start();
tt3.start();
}
}