What is wrong with this class?

AreYouDone.java

public class AreYouDone {
    private boolean done = false;

    public void done() {
        done = true;
    }

    public boolean isDone() {
        return done;
    }

    public static void main(String[] args) throws Exception {
        final AreYouDone areYouDone = new AreYouDone();
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1500);
                }
                catch (InterruptedException e) {
                    e.printStackTrace();
                }
                areYouDone.done();
            }
        }).start();
        while (!areYouDone.isDone()) {}
    }
}