解决线程并发安全问题

package cn.wlt.tickets;
/**
*
* @作者: CarryWang
* @描述: 买票窗口 100张票
*
*/
public class SaleTicket extends Thread{
private String name;
/**
* 100张票数共享的数据 属于类的属性
*/
private static int tickets=100;
//同步锁对象
private static Object obj=new Object();

public SaleTicket(String name) {
    super(name);
    this.name = name;
}


@Override
public void run() {
    while(true){
        /*
         * 锁  synchronized (name)  这个name对象一定得是共享对象
         * 同步代码块
         */
        synchronized (obj) {
            if(tickets>0){
                try {
                    //线程休息10毫秒
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(this.getName()+"正在卖第"+tickets--+"张票");
            }else{
                System.out.println("票已经售完");
                break;
            }
        }

    }
}

}

测试代码：
package cn.wlt.tickets;

import org.junit.Test;

public class TicketTest {

public static void main(String[] args) {
    SaleTicket st1=new SaleTicket("窗口1");
    SaleTicket st2=new SaleTicket("窗口2");
    SaleTicket st3=new SaleTicket("窗口3");
    SaleTicket st4=new SaleTicket("窗口4");
    st1.start();
    st2.start();
    st3.start();
    st4.start();
}

}