在JAVA中提供了同步机制，可以有效地防止资源冲突，同步机制使用synchronized关键字
pubic class CopyOfThreadSafeTest implements Runnable{
int num=10;
public void run(){
while(true){
synchronized(""){
if (num>0){
try{
Thread.slepp(1000);
}catch(Exception e){
e.printStackTrace();
}
System.out.println("tickets""+--num);
}
}
}
}
public static void main(String[] args){
CopyOfThreadSafeTest t=new CopyOfThreadSafeTest ();
Thread tA=new Thread(t);
Thread tB=new Thread(t);
Thread tC=new Thread(t);
Thread tD=new Thread(t);
tA.start();
tB.start();
tC.start();
tD.start();
}
}