Java SE 多线程 线程生命周期

package thread;
class ThreadTest4 implements Runnable{
 private boolean flag=true;
 public void stopMe(){
  flag=false;
 }
 public void run() {
  while (flag){
   System.out.println(Thread.currentThread().getName()+" is running ");
  } 
 }
}
public class ThreadLife {
 public static void main(String[] args) {
  ThreadTest4 tt4=new ThreadTest4();
  new Thread(tt4).start();
  for(int i=0;i<100;i++){
   if(i==50)
    tt4.stopMe();
   System.out.println("i="+i+"   "+Thread.currentThread().getName()+" is running ");
  }
 }
}