JVM : Daemon and Non-Daemon Thread

Daemon and Non-Daemon threads are created via JVM. Main method is non-daemon thread or user thread that are terminated automatically when all non-daemon threads in the program have finished or when the main application exits.

If you want to create any non-daemon thread as daemon then we can set as setDaemon(true).

Examples of daemon threads include the garbage collector in Java or background service threads in server applications.

Non-daemon threads keep the application alive until they complete their task or are explicitly terminated.

In summary, daemon and non-daemon threads serve different purposes in a multithreaded application, with daemon threads typically performing background tasks and non-daemon threads handling critical application functionality.

public class DaemonExample {
    public static void main(String[] args) {
        // Creating a daemon thread
        Thread daemonThread = new Thread(() -> {
            while (true) {
                System.out.println("Daemon thread is running");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        daemonThread.setDaemon(true); // Set the thread as daemon
        daemonThread.start();

        // Creating a non-daemon thread
        Thread nonDaemonThread = new Thread(() -> {
            int count = 0;
            while (count < 5) {
                System.out.println("Non-daemon thread is running");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                count++;
            }
        });
        nonDaemonThread.start();

        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Main thread exiting");
    }
}