How to open another program with for statements java?

Question

I'm very new to java I have been doing basic stuff and for my final project we wanted to create a gui rpg. Our problem right now is we can't figure out how to open another program by clicking the gui button. My friends told me you guys use eclipse so I don't have to show imports. Keep in mind I'm in highschool so don't judge too harsh :D Here is our code:

public class Narnia {

    private static final String BACKHGROUND_IMAGE_URL = "http://randomwallpapers.net/fantasy-castle-1920x1080-wallpaper328374.jpg";

    protected void initUI() throws MalformedURLException {
        JFrame frame = new JFrame(Narnia.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final ImageIcon backgroundImage = new ImageIcon(new URL(BACKHGROUND_IMAGE_URL));

        JLabel mainPanel = new JLabel(backgroundImage) {
            @Override
            public Dimension getPreferredSize() {
                Dimension size = super.getPreferredSize();
                Dimension lmPrefSize = getLayout().preferredLayoutSize(this);
                size.width = Math.max(size.width, lmPrefSize.width);
                size.height = Math.max(size.height, lmPrefSize.height);
                return size;
            }
        };

        mainPanel.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(10, 10, 10, 10);
        gbc.weightx = 1.0;
        gbc.anchor = GridBagConstraints.WEST;
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        for (int i = 0; i < 1; i++) {
            mainPanel.add(new JButton("Play" + ("")), gbc);
        }
        for (int i = 0; i < 1; i++) {
            mainPanel.add(new JButton("Credits " + ("")), gbc);
        }
        for (int i = 0; i < 1; i++) {
            mainPanel.add(new JButton("Exit " + ("")), gbc);
        }

        // Let's put a filler bottom component that will push the rest to the top
        gbc.weighty = 1.0;
        mainPanel.add(Box.createGlue(), gbc);
        frame.add(mainPanel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                try {
                    new Narnia().initUI();
                    } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });
    }
}

Here is the class we want to open:

public class chooseaclass {

    private static final String BACKHGROUND_IMAGE_URL = "http://randomwallpapers.net/fantasy-castle-1920x1080-wallpaper328374.jpg";

    protected void initUI() throws MalformedURLException {
        JFrame frame = new JFrame(chooseaclass.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final ImageIcon backgroundImage = new ImageIcon(new URL(BACKHGROUND_IMAGE_URL));

        JLabel mainPanel = new JLabel(backgroundImage) {
            @Override
            public Dimension getPreferredSize() {
                Dimension size = super.getPreferredSize();
                Dimension lmPrefSize = getLayout().preferredLayoutSize(this);
                size.width = Math.max(size.width, lmPrefSize.width);
                size.height = Math.max(size.height, lmPrefSize.height);
                return size;
            }
        };

        mainPanel.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(40, 40, 40, 40);
        gbc.weightx = 1.0;
        gbc.anchor = GridBagConstraints.CENTER;
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        for (int i = 0; i < 1; i++) {
            mainPanel.add(new JButton("Archer" + ("")), gbc);
        }
        for (int i = 0; i < 1; i++) {
            mainPanel.add(new JButton("Mage " + ("")), gbc);
        }
        for (int i = 0; i < 1; i++) {
            mainPanel.add(new JButton("Knight " + ("")), gbc);
        }

        // Let's put a filler bottom component that will push the rest to the top
        gbc.weighty = 1.0;
        mainPanel.add(Box.createGlue(), gbc);
        frame.add(mainPanel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                try {
                    new chooseaclass().initUI();
                    } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });
    }
}

Answer 1

You need to add a listener to whatever button you want. In this case, we'll use an ActionListener.

Let's just use this existing line that you already have: mainPanel.add(new JButton("Play" + ("")), gbc);

First of all, to make it simpler, let's put that JButton in a variable: JButton playButton = new JButton("Play" + (""));

To add a listener, we need to use the method addActionListener().

Now add an ActionListener as an anonymous class so that we can implement a method that the system can call behind the scenes:

JButton playButton = new JButton("Play" + (""));
    playButton.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            new chooseaclass.initUI() //insantiate a new chooseaclass instance

        }

    });
    mainPanel.add(playButton, gbc);

Within the actionPerformed() method, I instantiated a chooseaclass. You can do whatever you want from there.

I wrote this code off the cuff without an editor so it may contain syntax errors.