1.9yield方法

yield()方法的作用放弃当前的cpu资源，将他让给其他的任务去占用cpu的执行时间，但放弃的时间不确定，有可能刚放弃，马上又获得cpu时间片

测试

 package com.cky.thread;

 /**
  * Created by edison on 2017/12/3.
  */
 public class MyThread3 extends Thread{
     @Override
     public void run() {
         super.run();
         long begin = System.currentTimeMillis();
         int count =0;
         for (int i = 0; i < 5000000; i++) {
             //Thread.yield();
             count=count+(i+1);
         }
         long end = System.currentTimeMillis();
         System.out.println("用时" +(end-begin)+"毫秒");
     }
 }

 package com.cky.test;

 import com.cky.thread.MyThread3;

 /**
  * Created by edison on 2017/12/3.
  */
 public class Test3 {
     public static void main(String[] args) {
         MyThread3 th = new MyThread3();
         th.start();
     }
 }

package com.cky.thread;

/**
 * Created by edison on 2017/12/3.
 */
public class MyThread3 extends Thread{
    @Override
    public void run() {
        super.run();
        long begin = System.currentTimeMillis();
        int count =0;
        for (int i = 0; i < 5000000; i++) {
            Thread.yield();
            count=count+(i+1);
        }
        long end = System.currentTimeMillis();
        System.out.println("用时" +(end-begin)+"毫秒");
    }
}

上述两种情况运行结果

有注释：48毫秒

无注释：11100毫秒

结果说明了他放弃当前的cpu资源。