Java Java.lang.ThreadGroup.setDaemon()用法及代碼示例

描述

這個java.lang.ThreadGroup.setDaemon()方法更改此線程組的守護進程狀態。守護線程組在其最後一個線程停止或最後一個線程組被銷毀時自動銷毀。

聲明

以下是聲明java.lang.ThreadGroup.setDaemon()方法

public final void setDaemon(boolean daemon)

參數

daemon- 如果為真，則將此線程組標記為守護線程組；否則，將此線程組標記為正常。

返回值

此方法不返回任何值。

異常

SecurityException- 如果當前線程不能修改這個線程組。

示例

下麵的例子展示了 java.lang.ThreadGroup.setDaemon() 方法的用法。

package com.tutorialspoint;

import java.lang.*;

public class ThreadGroupDemo implements Runnable {
   public static void main(String[] args) {
      ThreadGroupDemo tg = new ThreadGroupDemo();
      tg.func();
   }

   public void func() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pGroup = new ThreadGroup("Parent ThreadGroup");
         // daemon status is set to true
         pGroup.setDaemon(true);
    
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cGroup = new ThreadGroup(pGroup, "Child ThreadGroup");
         // daemon status is set to true
         cGroup.setDaemon(true);

         // create a thread
         Thread t1 = new Thread(pGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(cGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         // returns true if this thread group is a daemon thread group
         System.out.println("Is " + pGroup.getName() + " a daemon
            ThreadGroup? " + pGroup.isDaemon());
         System.out.println("Is " + cGroup.getName() + " a daemon
            ThreadGroup? " + cGroup.isDaemon());

         // block until the other threads finish
         t1.join();
         t2.join();
      } catch (InterruptedException ex) {
         System.out.println(ex.toString());
      }
   }

   // implements run()
   public void run() {

      for(int i = 0;i < 1000;i++) {
         i++;
      }
      System.out.println(Thread.currentThread().getName() + 
         " finished executing.");
   }
}

讓我們編譯並運行上麵的程序，這將產生以下結果 -

Starting Thread-0...
Starting Thread-1...
Is Parent ThreadGroup a daemonThreadGroup? true
Is Child ThreadGroup a daemonThreadGroup? true
Thread-0 finished executing.
Thread-1 finished executing.