Does a child thread in Java prevent the parent threads to terminate?

Question

When I create and start a thread inside another thread, will it be a child thread? Does it prevent the termination of the parent thread while the child thread is running? For example:

new Thread(new Runnable() {
    @Override
    public void run() {
        //Do Sth
        new Thread(new Runnable() {
            @Override
            public void run() {
                //Do Sth
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        //Do Sth
                    }
                }).start();
                //Do Sth
            }
        }).start();
        //Do Sth
    }
    //Do Sth            
}).start();

Answer 1

In your code, there is a parent-child relationship between objects. However, there is no notion of a parent-child relationship between threads. Once the two threads are running they're basically peers.

Let's say that thread A starts thread B. Unless there's explicit synchronisation between them, either thread can terminate whenever it pleases without affecting the other thread.

Note that either thread can keep the process alive for as long as the thread lives. See What is Daemon thread in Java?