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();  }}