Question

I am trying to implement a music player.
I wrote a class which extends from Thread and overwrote its Start()-Method to play a random song.

Playing a song works, but I want to send that thread to the background, which doesn’t work:

File file = new File("song.mp3");
PlayEngine plengine = new PlayEngine(); //This class extends from Thread

plengine.Play(file); //This just sets the file to play in a variable
plengine.Start(); //And this finally plays the file itself

System.out.println("Next task:"); // I don't get to this point. Only when the song has finished.

As you can see in the code above, I’d like to go to the printed line right after launching the thread.

Answer 1

It is not recommended to extend Thread – Have your PlayEngine implement Runnable instead, and override the run method:

class PlayEngine implements Runnable {
    private final File file;

    PlayEngine(File file) {
        this.file = file;
    }

    @Override
    public void run() {
        //do your stuff here
        play(file);
    }
}

Then start the tread with:

PlayEngine plengine = new PlayEngine(file);
Thread t = new Thread(plengine);
t.start();
System.out.println("Next task:");

and Next task should print immediately. In your example, you seem to be calling the long running method play in the main thread, which explains why it does not return immediately.