Create a Chess board with JPanel [duplicate]

Question

Note

The GUI seen here has been improved and moved to Making a robust, resizable Swing Chess GUI.

I will leave the animated GIF here (because it's cute) and the original, stripped down code (of just 125 code lines, the final code seen on the other thread is 218 LOC).

Chess Game Layout

import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.*;

public class ChessBoardWithColumnsAndRows {

    private final JPanel gui = new JPanel(new BorderLayout(3, 3));
    private JButton[][] chessBoardSquares = new JButton[8][8];
    private JPanel chessBoard;
    private final JLabel message = new JLabel(
            "Chess Champ is ready to play!");
    private static final String COLS = "ABCDEFGH";

    ChessBoardWithColumnsAndRows() {
        initializeGui();
    }

    public final void initializeGui() {
        // set up the main GUI
        gui.setBorder(new EmptyBorder(5, 5, 5, 5));
        JToolBar tools = new JToolBar();
        tools.setFloatable(false);
        gui.add(tools, BorderLayout.PAGE_START);
        tools.add(new JButton("New")); // TODO - add functionality!
        tools.add(new JButton("Save")); // TODO - add functionality!
        tools.add(new JButton("Restore")); // TODO - add functionality!
        tools.addSeparator();
        tools.add(new JButton("Resign")); // TODO - add functionality!
        tools.addSeparator();
        tools.add(message);

        gui.add(new JLabel("?"), BorderLayout.LINE_START);

        chessBoard = new JPanel(new GridLayout(0, 9));
        chessBoard.setBorder(new LineBorder(Color.BLACK));
        gui.add(chessBoard);

        // create the chess board squares
        Insets buttonMargin = new Insets(0,0,0,0);
        for (int ii = 0; ii < chessBoardSquares.length; ii++) {
            for (int jj = 0; jj < chessBoardSquares[ii].length; jj++) {
                JButton b = new JButton();
                b.setMargin(buttonMargin);
                // our chess pieces are 64x64 px in size, so we'll
                // 'fill this in' using a transparent icon..
                ImageIcon icon = new ImageIcon(
                        new BufferedImage(64, 64, BufferedImage.TYPE_INT_ARGB));
                b.setIcon(icon);
                if ((jj % 2 == 1 && ii % 2 == 1)
                        //) {
                        || (jj % 2 == 0 && ii % 2 == 0)) {
                    b.setBackground(Color.WHITE);
                } else {
                    b.setBackground(Color.BLACK);
                }
                chessBoardSquares[jj][ii] = b;
            }
        }

        //fill the chess board
        chessBoard.add(new JLabel(""));
        // fill the top row
        for (int ii = 0; ii < 8; ii++) {
            chessBoard.add(
                    new JLabel(COLS.substring(ii, ii + 1),
                    SwingConstants.CENTER));
        }
        // fill the black non-pawn piece row
        for (int ii = 0; ii < 8; ii++) {
            for (int jj = 0; jj < 8; jj++) {
                switch (jj) {
                    case 0:
                        chessBoard.add(new JLabel("" + (ii + 1),
                                SwingConstants.CENTER));
                    default:
                        chessBoard.add(chessBoardSquares[jj][ii]);
                }
            }
        }
    }

    public final JComponent getChessBoard() {
        return chessBoard;
    }

    public final JComponent getGui() {
        return gui;
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {
                ChessBoardWithColumnsAndRows cb =
                        new ChessBoardWithColumnsAndRows();

                JFrame f = new JFrame("ChessChamp");
                f.add(cb.getGui());
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                f.setLocationByPlatform(true);

                // ensures the frame is the minimum size it needs to be
                // in order display the components within it
                f.pack();
                // ensures the minimum size is enforced.
                f.setMinimumSize(f.getSize());
                f.setVisible(true);
            }
        };
        SwingUtilities.invokeLater(r);
    }
}

Notes

The chess board complete with columns on the left and a row above it is provided by a 9x9 GridLayout. The first cell of the grid layout is a label with no text.
To simplify the game logic though, we maintain a separate 8x8 array of buttons.
To allow keyboard functionality we use buttons for the chess board places. This also provides inbuilt focus indication. Remove the margin of the button to allow them to shrink to the size of the icon. Add an ActionListener to the button and it will respond to both keyboard and mouse events.
The small ? in the left hand side of the GUI is meant to imply that area is 'reserved for future use'. We might use it to show lists of captured pieces, a selector for choice of piece when promoting pawns, game statistics, ...
The chess piece images were obtained from Example images for code and mark-up Q&As, which was in turn developed out of 'Fill' Unicode characters in labels.

Using images is simpler, whereas filling Unicode characters is more versatile as well as being 'lighter'. I.E. to support 4 different colors in 3 separate sizes of 3 different chess piece styles would require 36 separate sprite sheets!