如何监控线程的状态？（How to monitor a thread's status?）

问题描述 (Problem Description)

如何监控线程的状态？

解决方案 (Solution)

下面的示例演示如何通过扩展Thread类和使用currentThread.getName（）方法来监视线程的状态。

class MyThread extends Thread {
   boolean waiting = true;
   boolean ready = false;
   MyThread() {
   }
   public void run() {
      String thrdName = Thread.currentThread().getName();
      System.out.println(thrdName + " starting.");
      while(waiting) System.out.println("waiting:"+waiting); 
      System.out.println("waiting...");
      startWait(); 
      try {
         Thread.sleep(1000);
      } catch(Exception exc) {
         System.out.println(thrdName + " interrupted.");
      }
      System.out.println(thrdName + " terminating.");
   }
   synchronized void startWait() {
      try {
         while(!ready) wait();
      } catch(InterruptedException exc) {
         System.out.println("wait() interrupted");
      }
   }
   synchronized void notice() {
      ready = true;
      notify();
   }
}
public class new_class {
   public static void main(String args[]) throws Exception {
      MyThread thrd = new MyThread();
      thrd.setName("MyThread #1");
      showThreadStatus(thrd);
      thrd.start();
      Thread.sleep(50);
      showThreadStatus(thrd);
      thrd.waiting = false;
      Thread.sleep(50); 
      showThreadStatus(thrd);
      thrd.notice();
      Thread.sleep(50);
      showThreadStatus(thrd);
      while(thrd.isAlive()) 
      System.out.println("alive");
      showThreadStatus(thrd);
   }
   static void showThreadStatus(Thread thrd) {
      System.out.println(thrd.getName()+"  Alive:="+thrd.isAlive()+" State:=" + thrd.getState() );
   }
}

结果 (Result)

上面的代码示例将产生以下结果。

main Alive=true State:=running