Daemon thread in Java

A daemon thread is a thread, that does not prevent the JVM from exiting when the program finishes but the thread is still running.

An example for a daemon thread is the garbage collection.

You can use the setDaemon() method to change the Thread daemon properties.

setDamon(boolean) can only be called before the thread has been started.

By default the thread inherits the daemon status of its parent thread.

• When a new thread is created it inherits the daemon status of its parent.
• Normal thread and daemon threads differ in what happens when they exit.                           When the JVM halts any remaining daemon threads are abandoned: finally blocks are not executed, stacks are not unwound - JVM just exits. Due to this reason daemon threads should be used sparingly and it is dangerous to use them for tasks that might perform any sort of I/O.

public class DaemonTest

{

  public static void main(String[] args)

  {

     new WorkerThread().start();

     try 

     {

         Thread.sleep(7500);

     }

     catch (InterruptedException e)

     {}

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

  }

}

class WorkerThread extends Thread

{

  public WorkerThread()

  {

     setDaemon(true) ; // 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.

   }

   public void run()

   {

      int count=0 ;

      while (true)

     {

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

         try

        {

           sleep(5000);

        }

        catch (InterruptedException e)

        {}

     }

  }

}