Java并发程序入门介绍

今天看了看Java并发程序，写一写入门程序，并设置了线程的优先级。

class Elem implements Runnable{
  public static int id = 0;
  private int cutDown = 5;
  private int priority;
  
  public void setPriority(int priority){
    this.priority = priority;
  }
  
  public int getPriority(){
    return this.priority;
  }
  public void run(){
    Thread.currentThread().setPriority(priority);
    int threadId = id++;
    while(cutDown-- > 0){
      double d = 1.2;
      while(d < 10000)
        d = d + (Math.E + Math.PI)/d;
      System.out.println("#" + threadId + "(" + cutDown + ")");
    }
  }
}
public class Basic {
  public static void main(String args[]){
    for(int i = 0; i < 10; i++){
      Elem e = new Elem();
      if(i == 0 )
        e.setPriority(Thread.MAX_PRIORITY);
      else
        e.setPriority(Thread.MIN_PRIORITY);
      Thread t = new Thread(e);
      t.start();
    }
  }
}

由于机器很强悍，所以先开始并没看到并发的效果，感觉是按顺序执行的，所以在中间加了浮点数的运算来延迟时间。

当然，main函数里面可以用Executors来管理线程。

import java.util.concurrent.*;
class Elem implements Runnable{
  public static int id = 0;
  private int cutDown = 5;
  private int priority;
  
  public void setPriority(int priority){
    this.priority = priority;
  }
  
  public int getPriority(){
    return this.priority;
  }
  public void run(){
    Thread.currentThread().setPriority(priority);
    int threadId = id++;
    while(cutDown-- > 0){
      double d = 1.2;
      while(d < 10000)
        d = d + (Math.E + Math.PI)/d;
      System.out.println("#" + threadId + "(" + cutDown + ")");
    }
  }
}
public class Basic {
  public static void main(String args[]){
//    for(int i = 0; i < 10; i++){
//      Elem e = new Elem();
//      if(i == 0 )
//        e.setPriority(Thread.MAX_PRIORITY);
//      else
//        e.setPriority(Thread.MIN_PRIORITY);
//      Thread t = new Thread(e);
//      t.start();
//    }
    ExecutorService exec = Executors.newCachedThreadPool();
    for(int i = 0; i < 10; i++){
      Elem e = new Elem();
      if(i == 0 )
        e.setPriority(Thread.MAX_PRIORITY);
      else
        e.setPriority(Thread.MIN_PRIORITY);
      exec.execute(e);
    }
    exec.shutdown();
  }
}