How can I create a new thread only if no other threads are currently open?

Question

This code creates and starts a thread:

new Thread() {
    @Override
    public void run() {
        try { player.play(); }
        catch ( Exception e ) { System.out.println(e); }
    }
}.start();

I'd like to modify this code so that the thread only starts if there are no other threads open at the time! If there are I'd like to close them, and start this one.

Answer 1

You can create an ExecutorService that only allows a single thread with the Executors.newSingleThreadExecutor method. Once you get the single thread executor, you can call execute with a Runnable parameter:

Executor executor = Executors.newSingleThreadExecutor();
executor.execute(new Runnable() { public void run() { /* do something */ } });