understanding Swing

App32Pix.java

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

/**
 * Created with IntelliJ IDEA.
 * User: seronis
 * Date: 10/30/12
 * Time: 10:04 PM
 */
public class App32Pix extends JFrame
{
    Color color = new Color(255,255,255);
    JLabel statusbar;
    MainPanel panel;

    public App32Pix(String s) {
        initUI(s);
    }

    public final void initUI(String s) {
        JMenuBar menubar = new JMenuBar();

        JMenu menu_file = new JMenu("File");
        {
            menu_file.setMnemonic(KeyEvent.VK_F);
        //    ImageIcon icon_exit = new ImageIcon(getClass().getResource("exit.png"));
        //    JMenuItem eMenuItem = new JMenuItem("Exit", icon_exit);
            JMenuItem eMenuItem = new JMenuItem("Exit");
            {
                eMenuItem.setMnemonic(KeyEvent.VK_X);
                eMenuItem.setToolTipText("Exit Application");
                eMenuItem.addActionListener(new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        System.exit(0);
                    }
                });
                menu_file.add(eMenuItem);
            }
            menubar.add(menu_file);
        }

        JMenu menu_color = new JMenu("Color");
        {
            menu_color.setMnemonic(KeyEvent.VK_C);
            JMenuItem eMenuItem;
            {
                eMenuItem = new JMenuItem("Black");
                eMenuItem.addActionListener(new ColorAL(0,0,0));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("White");
                eMenuItem.addActionListener(new ColorAL(255,255,255));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Red");
                eMenuItem.addActionListener(new ColorAL(255,0,0));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Orange");
                eMenuItem.addActionListener(new ColorAL(255,127,0));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Yellow");
                eMenuItem.addActionListener(new ColorAL(255,255,0));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Ochre");
                eMenuItem.addActionListener(new ColorAL(127,255,0));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Green");
                eMenuItem.addActionListener(new ColorAL(0,255,0));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Turqoise");
                eMenuItem.addActionListener(new ColorAL(0,255,127));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Cyan");
                eMenuItem.addActionListener(new ColorAL(0,255,255));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Cobalt");
                eMenuItem.addActionListener(new ColorAL(0,127,255));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Blue");
                eMenuItem.addActionListener(new ColorAL(0,0,255));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Purple");
                eMenuItem.addActionListener(new ColorAL(127,0,255));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Magenta");
                eMenuItem.addActionListener(new ColorAL(255,0,255));
                menu_color.add(eMenuItem);
            }
            {
                eMenuItem = new JMenuItem("Pink");
                eMenuItem.addActionListener(new ColorAL(255,0,127));
                menu_color.add(eMenuItem);
            }
            menubar.add(menu_color);
        }

        setJMenuBar(menubar);

        panel = new MainPanel();
        panel.setLayout(null);
        panel.setBounds(0,0,400,300);

        statusbar = new JLabel(" Statusbar");
        statusbar.setBorder(BorderFactory.createEtchedBorder(EtchedBorder.RAISED));
        panel.add(statusbar, BorderLayout.SOUTH);
        add(panel);

        addMouseMotionListener(panel);

        setTitle(s);
        pack();
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(400, 300);
    }
    @Override
    public boolean isResizable() {
        return true;
    }

    class MainPanel extends JPanel
        implements MouseMotionListener
    {
        @Override
        public void mouseDragged(MouseEvent e) {
            //
        }
        @Override
        public void mouseMoved(MouseEvent e) {
            statusbar.setText(" X: " + e.getX() + "  Y: " + e.getY() + "    "
             + "(" + insets.left + "/" + insets.right
             + " " + insets.top + "/" + insets.bottom
             + " " + getWidth() + "/" + getHeight()
             + ")"
            );
            repaint();
        }
        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            insets = getInsets();

            Graphics2D g2d = (Graphics2D) g;

            g2d.drawLine(0,0,230,230);
        }
        Insets insets;
    }

    class ColorAL implements ActionListener {
        Color temp;
        ColorAL(int r, int g, int b) {
            temp = new Color(r,g,b);
        }
        public void actionPerformed(ActionEvent e) {
            color = temp;
            panel.setBackground(color);
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                App32Pix window = new App32Pix("32px Editor by Seronis");
                window.setVisible(true);
            }
        });
    }
}