The daemon threads are typically used to perform services for user threads. The main() method of the application thread is a user thread (non-daemon thread). The JVM doesn’t terminate unless all the user thread (non-daemon) terminates. We can explicitly specify a thread created by a user thread to be a daemon thread by calling setDaemon(true). To determine if a thread is a daemon thread by using the method isDaemon().
Example
public class UserDaemonThreadTest extends Thread { public static void main(String args[]) { System.out.println("Thread name is : "+ Thread.currentThread().getName()); // Check whether the main thread is daemon or user thread System.out.println("Is main thread daemon ? : "+ Thread.currentThread().isDaemon()); UserDaemonThreadTest t1 = new UserDaemonThreadTest(); UserDaemonThreadTest t2 = new UserDaemonThreadTest(); // Converting t1(user thread) to a daemon thread t1.setDaemon(true); t1.start(); t2.start(); } public void run() { // Checking threads are daemon or not if (Thread.currentThread().isDaemon()) { System.out.println(Thread.currentThread().getName()+" is a Daemon Thread"); } else { System.out.println(Thread.currentThread().getName()+" is an User Thread"); } } }
Output
Thread name is : main Is main thread daemon ? : false Thread-0 is a Daemon Thread Thread-1 is an User Thread