JAVA的sleep

JAVA的sleep方法让出CPU，给其他线程运行机会：

package synsleep;
public class Machine implements Runnable {
  private int a=1;  //共享数据
  public void run() {
    for(int i=0;i<1000;i++){
      synchronized(this){
        a+=i;
        try{
          Thread.sleep(500); //给其他线程运行的机会
        }catch(InterruptedException e){throw new RuntimeException(e);}
        a-=i;
        System.out.println(Thread.currentThread().getName()+":"+a);
      }
    }
  }

  public void go(){
    for(int i=0;i<1000;i++){
        System.out.println(Thread.currentThread().getName()+":"+i);
        Thread.yield();
     }
  }
  public static void main(String args[]) throws InterruptedException{
    Machine machine=new Machine();
    Thread t1=new Thread(machine);
    Thread t2=new Thread(machine);
    t1.start();
    t2.start();
    machine.go();
  }
}