Difference between a daemon thread and a low priority thread

Question

Recently I was asked a question:

We\'ve got the setPriority() method to set a thread for low priority. Then why do we need a daemon thr

Answer 1

An example of

1. JVM shutting down when low priority thread completes. Despite Daemon threads still running

2. ALSO, shows that thread created by a daemon thread automatically becomes a daemon thread

   package junk.daemon_thread_example;
   
   class DeamonThreadPlus implements Runnable{
       String id;
       boolean createChild;
   
       public DeamonThreadPlus(String id, boolean createChild){
           this.id = id;
           this.createChild = createChild;
       }
   
       @Override
       public void run() {
           // Parent daemon thread creates child daemon thread by default
           if (createChild)
               new Thread(new DeamonThreadPlus("DaemonChild", false)).start();
   
           // This thread never self-completes (only terminates when process dies)
           while (true){
               try {
                   Thread.sleep(1);
               } catch (InterruptedException e) {
                   e.printStackTrace();
               }
               System.out.println("Daemon " 
                       + Thread.currentThread().isDaemon()
                       + " id = " + id);
               }
       }
   }
   
   class UThread implements Runnable{
   
       @Override
       public void run() {
           System.out.println("User thread start");
           try {
               Thread.sleep(5);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }
           System.out.println("User thread end (program exits)");
       }
   }
   
   public class Caller{
   
       public static void main(String[] args) {
           Thread dt = new Thread( new DeamonThreadPlus("Daemon", true));
           dt.setDaemon(true);
           dt.start();
   
           Thread ut = new Thread(new UThread());
           ut.setPriority(Thread.MIN_PRIORITY);
           ut.start(); 
       }
   
   }
   

   The output is: User thread start
   Daemon true id = Daemon
   Daemon true id = DaemonChild
   Daemon true id = Daemon
   Daemon true id = DaemonChild
   Daemon true id = Daemon
   Daemon true id = DaemonChild
   Daemon true id = Daemon
   Daemon true id = DaemonChild
   User thread end (program exits)
   Daemon true id = DaemonChild
   Daemon true id = Daemon