Can you explain what a demon thread is and how it differs from a regular thread?

A daemon thread in Java is a background thread that does not prevent the JVM from exiting. The main difference from a regular (user) thread is that the JVM automatically terminates when all user threads have finished, even if daemon threads are still running.

Features of daemon threads:

• They are intended for background tasks, such as garbage collection.
• They do not block the program from terminating.
• You can set a thread as a daemon using the setDaemon(true) method before starting the thread.

Example:

Thread daemonThread = new Thread(() -> {
    while (true) {
        System.out.println("Daemon thread is running");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            break;
        }
    }
});
daemonThread.setDaemon(true);
daemonThread.start();

System.out.println("Main thread has finished");

In this example, when the main thread finishes, the JVM will automatically stop the daemon thread.