Java 守护线程

When the JVM halts any remaining daemon threads are abandoned:

 1. finally blocks are not executed,
 2. stacks are not unwound - the JVM just exits.

public class DaemonTest {

    public static void main(String[] args) {
        new WorkerThread().start();

        try {
            Thread.sleep(7500);
        } catch (InterruptedException e) {
            // handle here exception
        }

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

}

class WorkerThread extends Thread {

    public WorkerThread() {
        // 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.
        setDaemon(false);
    }

    public void run() {
        int count = 0;

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

            try {
                sleep(5000);
            } catch (InterruptedException e) {
                // handle exception here
            }
        }
    }
}

Hello from Worker 0
Hello from Worker 1
Main Thread ending
Hello from Worker 2
Hello from Worker 3
Hello from Worker 4
Hello from Worker 5
....

Hello from Worker 0
Hello from Worker 1
Main Thread ending