Show JFrame in a specific screen in dual monitor configuration

public static void showOnScreen( int screen, JFrame frame )
{
    GraphicsEnvironment ge = GraphicsEnvironment
        .getLocalGraphicsEnvironment();
    GraphicsDevice[] gs = ge.getScreenDevices();
    if( screen > -1 && screen < gs.length )
    {
        gs[screen].setFullScreenWindow( frame );
    }
    else if( gs.length > 0 )
    {
        gs[0].setFullScreenWindow( frame );
    }
    else
    {
        throw new RuntimeException( "No Screens Found" );
    }
}

I have modified @Joseph-gordon's answer to allow for a way to achieve this without forcing full-screen:

public static void showOnScreen( int screen, JFrame frame ) {
    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] gd = ge.getScreenDevices();
    if( screen > -1 && screen < gd.length ) {
        frame.setLocation(gd[screen].getDefaultConfiguration().getBounds().x, frame.getY());
    } else if( gd.length > 0 ) {
        frame.setLocation(gd[0].getDefaultConfiguration().getBounds().x, frame.getY());
    } else {
        throw new RuntimeException( "No Screens Found" );
    }
}

In this code I am assuming getDefaultConfiguration() will never return null. If that is not the case then someone please correct me. But, this code works to move your JFrame to the desired screen.

A much cleaner solution after reading the docs for JFrame.setLocationRelativeTo Display on screen 2

public void moveToScreen() {
    setVisible(false);
    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] screens = ge.getScreenDevices();
    int n = screens.length;
    for (int i = 0; i < n; i++) {
        if (screens[i].getIDstring().contentEquals(settings.getScreen())) {
            JFrame dummy = new JFrame(screens[i].getDefaultConfiguration());
            setLocationRelativeTo(dummy);
            dummy.dispose();
        }
    }
    setVisible(true);
}

This function can be used to switch application window between screens

I have modified @Joseph-gordon and @ryvantage answer to allow for a way to achieve this without forcing full-screen, fixed screen configuration position and center it on select screen:

public void showOnScreen(int screen, JFrame frame ) {
    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] gd = ge.getScreenDevices();
    int width = 0, height = 0;
    if( screen > -1 && screen < gd.length ) {
        width = gd[screen].getDefaultConfiguration().getBounds().width;
        height = gd[screen].getDefaultConfiguration().getBounds().height;
        frame.setLocation(
            ((width / 2) - (frame.getSize().width / 2)) + gd[screen].getDefaultConfiguration().getBounds().x, 
            ((height / 2) - (frame.getSize().height / 2)) + gd[screen].getDefaultConfiguration().getBounds().y
        );
        frame.setVisible(true);
    } else {
        throw new RuntimeException( "No Screens Found" );
    }
}

Please Refer to GraphicsDevice API, you have a good example there.