triple screen setup won't work

Question

so I'm making a program with a "controller" and two display screen's, kinda like Powerpoint when you press slideshow its open on the second screen in fullscreen. I have manage to do it with only two screens but every time I try with three I get a null pointer. here is my code:

import javax.imageio.ImageIO;

public class Program extends Canvas implements Runnable{
private static final long serialVersionUID = -7579474834886333524L;

private Thread thread;
private boolean isRunning = false;

private Måler måler;
private MålerLille målerlille;

public Program() {
    new Controller();

    målerlille = new MålerLille(1920, 1080, "screen3", this);
    måler = new Måler(1920, 1080, "screen2", this);

    GraphicsEnvironment ge = GraphicsEnvironment .getLocalGraphicsEnvironment();
    GraphicsDevice[] gs = ge.getScreenDevices();

    gs[2].setFullScreenWindow(MålerLille.frameML);
    gs[1].setFullScreenWindow(Måler.frame);