Gomoku.java

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

/**
 * <code>Gomoku</code> - a simple GUI for playing basic Gomoku. See
 * http://en.wikipedia.org/wiki/Gomoku
 *
 * Usage: java Gomoku [<grid size>]
 * @author Todd W. Neller
 * @version 1.0
 */
public class Gomoku
{
    /**
     * <code>main</code> - Create the JFrame and start a new embedded
     * Gomoku game.  The grid size is 19 by default, but may be
     * supplied in the first command line argument.
     *
     * @param args a <code>String[]</code> value - command line
     * arguments
     */
    public static void main(String[] args) {

	int size = 19;
	if (args.length > 0)
	    size = Integer.parseInt(args[0]);

	JFrame frame = new JFrame();
	
	final int FRAME_WIDTH = 600;
	final int FRAME_HEIGHT = 650;
	frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
	frame.setTitle("Gomoku");
	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	
	GomokuPanel panel = new GomokuPanel(size);
	frame.add(panel);
	
	frame.setVisible(true);
    }
}

class GomokuPanel extends JPanel
{
    private final int MARGIN = 5;
    private final double PIECE_FRAC = 0.9;

    private int size = 19;
    private GomokuState state;
    
    public GomokuPanel() 
    {
	this(19);
    }

    public GomokuPanel(int size) 
    {
	super();
	this.size = size;
	state = new GomokuState(size);
	addMouseListener(new GomokuListener());
    }

    class GomokuListener extends MouseAdapter 
    {
	public void mouseReleased(MouseEvent e) 
	{
	    double panelWidth = getWidth();
	    double panelHeight = getHeight();
	    double boardWidth = Math.min(panelWidth, panelHeight) - 2 * MARGIN;
	    double squareWidth = boardWidth / size;
	    double pieceDiameter = PIECE_FRAC * squareWidth;
	    double xLeft = (panelWidth - boardWidth) / 2 + MARGIN;
	    double yTop = (panelHeight - boardWidth) / 2 + MARGIN;
	    int col = (int) Math.round((e.getX() - xLeft) / squareWidth - 0.5);
	    int row = (int) Math.round((e.getY() - yTop) / squareWidth - 0.5);
	    if (row >= 0 && row < size && col >= 0 && col < size
		&& state.getPiece(row, col) == GomokuState.NONE
		&& state.getWinner() == GomokuState.NONE) {
		state.playPiece(row, col);
		repaint();
		int winner = state.getWinner();
		if (winner != GomokuState.NONE)
		    JOptionPane.showMessageDialog(null,
                      (winner == GomokuState.BLACK) ? "Black wins!" 
						    : "White wins!");
	    }
	}    
    }
    
    
    public void paintComponent(Graphics g) 
    {
	Graphics2D g2 = (Graphics2D) g;
	g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
			    RenderingHints.VALUE_ANTIALIAS_ON);
	
	double panelWidth = getWidth();
	double panelHeight = getHeight();

	g2.setColor(new Color(0.925f, 0.670f, 0.34f)); // light wood
	g2.fill(new Rectangle2D.Double(0, 0, panelWidth, panelHeight));

	
	double boardWidth = Math.min(panelWidth, panelHeight) - 2 * MARGIN;
	double squareWidth = boardWidth / size;
	double gridWidth = (size - 1) * squareWidth;
	double pieceDiameter = PIECE_FRAC * squareWidth;
	boardWidth -= pieceDiameter;
	double xLeft = (panelWidth - boardWidth) / 2 + MARGIN;
	double yTop = (panelHeight - boardWidth) / 2 + MARGIN;

	g2.setColor(Color.BLACK);
	for (int i = 0; i < size; i++) {
	    double offset = i * squareWidth;
	    g2.draw(new Line2D.Double(xLeft, yTop + offset, 
				      xLeft + gridWidth, yTop + offset));
	    g2.draw(new Line2D.Double(xLeft + offset, yTop,
				      xLeft + offset, yTop + gridWidth));
	}
	
	for (int row = 0; row < size; row++) 
	    for (int col = 0; col < size; col++) {
		int piece = state.getPiece(row, col);
		if (piece != GomokuState.NONE) {
		    Color c = (piece == GomokuState.BLACK) ? Color.BLACK : Color.WHITE;
		    g2.setColor(c);
		    double xCenter = xLeft + col * squareWidth;
		    double yCenter = yTop + row * squareWidth;
		    Ellipse2D.Double circle
			= new Ellipse2D.Double(xCenter - pieceDiameter / 2,
					       yCenter - pieceDiameter / 2,
					       pieceDiameter,
					       pieceDiameter);
		    g2.fill(circle);
		    g2.setColor(Color.black);
		    g2.draw(circle);
		}
	    }
    }
}