Java 多线程优先级实例详解

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class SimplePriorities implements Runnable {

  private int countDown = 5;

  /*Java语言规范第三版中对volatile的定义如下： java编程语言允许线程访问共享变量，
  为了确保共享变量能被准确和一致的更新，线程应该确保通过排他锁单独获得这个变量。
  Java语言提供了volatile，在某些情况下比锁更加方便。如果一个字段被声明成volatile，
  java线程内存模型确保所有线程看到这个变量的值是一致的。*/
  private volatile double d;
  private int priority;

  public SimplePriorities(int priority){
    this.priority = priority;
  }

  public String toString(){
    //获取当前线程信息
    return Thread.currentThread() + ":" + countDown;
  }

  @Override
  public void run() {
    //设置线程优先级 1-10
    Thread.currentThread().setPriority(priority);

    while(true){

      for(int i = 0;i<100000;i++){
        d += (Math.PI + Math.E) / (double)i;
        if(i00 == 0){
          Thread.yield();
        }
      }
      System.out.println(this.toString());

      if(--countDown == 0)return;

    }

  }

  public static void main(String[] args) {


    ExecutorService exec = Executors.newCachedThreadPool();

    //优先级为1
    exec.execute(new SimplePriorities(Thread.MIN_PRIORITY));
    //优先级为10
    exec.execute(new SimplePriorities(Thread.MAX_PRIORITY));

    exec.shutdown();
  }

}