PaintBox.java

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

public class PaintBox extends JFrame {
    private SlidePanel colorChooser;
    private JPanel colorView;
    private TopButtonPanel topPanel;
    private PaintPanel paintArea;

    /* the constructor */
    public PaintBox() {
        firstInit();
        init();
    }

    private void init() { // a helper method
        Container pane = getContentPane();

        /* the color chooser panel at the east side */
        JPanel eastPanel = new JPanel();

        /* A layout manager of the more complex kind */
        GridBagLayout gbl = new GridBagLayout();
        eastPanel.setLayout(gbl);
        GridBagConstraints gbc = new GridBagConstraints();

        colorChooser = new SlidePanel(this);
        gbc.gridx = 0; // first column
        gbc.gridy = 0; // first row
        eastPanel.add(colorChooser, gbc);

        colorView = new JPanel();
        colorView.setBackground(Color.black);
        gbc.gridx = 0; // first column
        gbc.gridy = 1; // second row
        gbc.ipadx = 90;
        gbc.ipady = 90;
        eastPanel.add(colorView, gbc);
        pane.add(eastPanel, "East");

        /* the buttons at the top */
        topPanel = new TopButtonPanel(this);
        pane.add(topPanel, "North");

        /* the main paint area */
        paintArea = new PaintPanel();
        pane.add(paintArea, "Center");
    }

    public void setColor(int r, int g, int b) {
        colorView.setBackground(new Color(r, g, b));
        paintArea.setColor(new Color(r, g, b));
    }

    public void setFilled(boolean b) {
        paintArea.setFilled(b);
    }

    public void setShape(int i) {
        paintArea.setShape(i);
    }

    /* A common GUI constructor helper method */
    private void firstInit() {
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });

        setTitle("PaintBox");
        setSize(600,400);

        /* Find the middle position on the screen */
        Dimension dim = Toolkit.getDefaultToolkit().
                                getScreenSize();
        int w = (dim.width - 600) / 2;
        int h = (dim.height -300) / 2;
        if (w < 0 || h < 0) {
            w = 0;
            h = 0;
        }
        setLocation(w, h);
    }

    public static void main(String[] arg) {
        PaintBox p = new PaintBox();
        p.show();
    }
}