让我们只讨论工作示例中的代码。我喜欢russ上面的回答，但为了消除我的疑虑，我稍微加强了一下。我运行了两次，一次工作线程设置为deamon true (deamon线程)，另一次设置为false(用户线程)。它确认守护线程在主线程结束时结束。

public class DeamonThreadTest {

public static void main(String[] args) {

    new WorkerThread(false).start();    //set it to true and false and run twice.

    try {
        Thread.sleep(7500);
    } catch (InterruptedException e) {
        // handle here exception
    }

    System.out.println("Main Thread ending");
    }
   }

   class WorkerThread extends Thread {

    boolean isDeamon;

    public WorkerThread(boolean isDeamon) {
        // When false, (i.e. when it's a user thread),
        // the Worker thread continues to run.
        // When true, (i.e. when it's a daemon thread),
        // the Worker thread terminates when the main
        // thread terminates.
        this.isDeamon = isDeamon;
        setDaemon(isDeamon);
    }

    public void run() {
        System.out.println("I am a " + (isDeamon ? "Deamon Thread" : "User Thread (none-deamon)"));

        int counter = 0;

        while (counter < 10) {
            counter++;
            System.out.println("\tworking from Worker thread " + counter++);

            try {
                sleep(5000);
            } catch (InterruptedException e) {
                // handle exception here
            }
        }
        System.out.println("\tWorker thread ends. ");
    }
}



result when setDeamon(true)
=====================================
I am a Deamon Thread
    working from Worker thread 0
    working from Worker thread 1
Main Thread ending

Process finished with exit code 0


result when setDeamon(false)
=====================================
I am a User Thread (none-deamon)
    working from Worker thread 0
    working from Worker thread 1
Main Thread ending
    working from Worker thread 2
    working from Worker thread 3
    working from Worker thread 4
    working from Worker thread 5
    working from Worker thread 6
    working from Worker thread 7
    working from Worker thread 8
    working from Worker thread 9
    Worker thread ends. 

Process finished with exit code 0

以上答案都是好的。下面是一个简单的小代码片段，以说明两者的区别。在setDaemon中分别尝试true和false值。

public class DaemonTest {
    
    public static void main(String[] args) {
        new WorkerThread().start();

        try {
            Thread.sleep(7500);
        } catch (InterruptedException e) {
            // handle here exception
        }

        System.out.println("Main Thread ending") ;
    }

}

class WorkerThread extends Thread {
    
    public WorkerThread() {
        // When false, (i.e. when it's a non daemon thread),
        // the WorkerThread continues to run.
        // When true, (i.e. when it's a daemon thread),
        // the WorkerThread terminates when the main 
        // thread or/and user defined thread(non daemon) terminates.
        setDaemon(true); 
    }
    
    public void run() {
        int count = 0;

        while (true) {
            System.out.println("Hello from Worker "+count++);

            try {
                sleep(5000);
            } catch (InterruptedException e) {
                // handle exception here
            }
        }
    }
}

Daemon thread is like daemon process which is responsible for managing resources,a daemon thread is created by the Java VM to serve the user threads. example updating system for unix,unix is daemon process. child of daemon thread is always daemon thread,so by default daemon is false.you can check thread as daemon or user by using "isDaemon()" method. so daemon thread or daemon process are basically responsible for managing resources. for example when you starting jvm there is garbage collector running that is daemon thread whose priority is 1 that is lowest,which is managing memory. jvm is alive as long as user thread is alive,u can not kill daemon thread.jvm is responsible to kill daemon threads.

传统上，UNIX中的守护进程是那些不断在后台运行的进程，就像Windows中的服务一样。

Java中的守护线程是不阻止JVM退出的线程。特别是当只剩下守护线程时，JVM将退出。您可以通过调用线程上的setDaemon()方法来创建一个。

读取Daemon线程。

守护线程就像一个普通的线程，除了JVM只会在其他非守护线程不存在时关闭。守护进程线程通常用于为应用程序执行服务。

当最后一个非守护进程线程执行完成时，JVM将完成这项工作。默认情况下，JVM将创建一个线程作为非守护进程，但我们可以通过setDaemon(true)方法将线程创建为守护进程。Daemon线程的一个很好的例子是GC线程，它将在所有非Daemon线程完成后立即完成它的工作。