Command Pattern Usefulness when using JComponents

Question

So, I\'m developing a program using the Swing library and I obviously have buttons and menu items. Some of these are supposed to do the same stuff, and I thought using the C

Answer 1

When two or more components are mean to do exactly the same thingy, one should look at Action, which reduces the duplicate code.

Small example for further help :

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ActionExample {

    private JFrame frame;
    private JButton button;
    private JMenuItem exitItem;
    private Action commonActions;

    private class CommonActions extends AbstractAction {

        public CommonActions(String title, String desc) {
            super(title);
            putValue(SHORT_DESCRIPTION, desc);
        }

        @Override
        public void actionPerformed(ActionEvent ae) {
            JOptionPane.showMessageDialog(frame,
                "Closing Frame", "Information", JOptionPane.INFORMATION_MESSAGE);
            frame.dispose();
        }
    };

    private void displayGUI() {
        frame = new JFrame("Action Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);                

        commonActions = new CommonActions("Exit", "To Exit the Application");

        JPanel contentPane = new JPanel();
        button = new JButton();
        button.setAction(commonActions);
        contentPane.add(button);

        frame.setJMenuBar(getMenuBar());
        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JMenuBar getMenuBar() {
        JMenuBar menuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("File");

        exitItem = new JMenuItem(commonActions);
        fileMenu.add(exitItem);
        menuBar.add(fileMenu);

        return menuBar;
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new ActionExample().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}

---

ADDED an example with SINGLETON PATTERN (though I am not sure of this approach(about how good this approach is))

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ActionExample {

    private JFrame frame;
    private JButton button;
    private JMenuItem exitItem;

    private void displayGUI() {
        frame = new JFrame("Action Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        CommonActions.setValues(frame);

        JPanel contentPane = new JPanel();
        button = new JButton();
        button.setAction(CommonActions.getInstance());
        contentPane.add(button);

        frame.setJMenuBar(getMenuBar());
        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JMenuBar getMenuBar() {
        JMenuBar menuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("File");

        exitItem = new JMenuItem(CommonActions.getInstance());
        fileMenu.add(exitItem);
        menuBar.add(fileMenu);

        return menuBar;
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new ActionExample().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}

class CommonActions extends AbstractAction {

    private static CommonActions commonActions = null;
    private static JFrame frame = null;

    static {
        try {
            commonActions = new CommonActions("Exit", "To Exit the Application");
        } catch (Exception e) {
            throw new RuntimeException("BINGO, an error");
        }
    }

    private CommonActions(String title, String desc) {
        super(title);
        putValue(SHORT_DESCRIPTION, desc);
    }

    public static CommonActions getInstance() {
        return commonActions;
    }

    public static void setValues(JFrame f) {
        frame = f;
    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        JOptionPane.showMessageDialog(frame,
            "Closing Frame", "Information", JOptionPane.INFORMATION_MESSAGE);
        frame.dispose();
    }
}