守护线程与非守护线程

[TOC]

概念

进程中会同时存在二种线程：也就是守护线程和非守护线程，当所有的非守护线程结束时，程序也就终止了，同时会杀死进程中的所有守护线程。反过来说，只要任何非守护线程还在运行，程序就不会终止。

将线程转换为守护线程可以通过调用Thread对象的setDaemon(true)方法来实现。但是必须在thread.start()之前设置

Main线程结束，其他线程一样可以正常运行。

public class ParentTest
{
 
    public static void main(String[] args)
    {
        System.out.println("parent thread begin ");
        
        ChildThread t1 = new ChildThread("thread1");
        ChildThread t2 = new ChildThread("thread2");
        t1.start();
        t2.start();
 
        System.out.println("parent thread over ");
    }
}
 
class ChildThread extends Thread
{
    private String name = null;
 
    public ChildThread(String name)
    {
        this.name = name;
    }
 
    @Override
    public void run()
    {
        System.out.println(this.name + "--child thead begin");
 
        try
        {
            Thread.sleep(500);
        }
        catch (InterruptedException e)
        {
            System.out.println(e);
        }
 
        System.out.println(this.name + "--child thead over");
    }
}
 
 
--程序运行结果如下:
parent thread begin 
parent thread over 
thread2--child thead begin
thread1--child thead begin
thread2--child thead over
thread1--child thead over

Main线程结束，其他线程也可以立刻结束，当且仅当这些子线程都是守护线程

public class ParentTest
{
 
    public static void main(String[] args)
    {
        System.out.println("parent thread begin ");
        
        ChildThread t1 = new ChildThread("thread1");
        ChildThread t2 = new ChildThread("thread2");
        t1.setDaemon(true);
        t2.setDaemon(true);
        
        t1.start();
        t2.start();
 
        System.out.println("parent thread over ");
    }
}
class ChildThread extends Thread
{
    private String name = null;
    public ChildThread(String name)
    {
        this.name = name;
    }
    @Override
    public void run()
    {
        System.out.println(this.name + "--child thead begin");
        try
        {
            Thread.sleep(500);
        }
        catch (InterruptedException e)
        {
            System.out.println(e);
        }
        System.out.println(this.name + "--child thead over");
    }
}
 
 执行结果如下：
parent thread begin
parent thread over
thread1--child thead begin
thread2--child thead begin