This code will draw the 3D board and handle mouse clicks

import javax.swing.*;
import java.awt.*;
import java.awt.event.*; //This is needed for the mouse events

public class SampleGraphicsWindow extends JFrame { //JFrame means "window", in effect
 
  private JPanel wholeWindow; //A JPanel is the content within a window
  private int width, height;  //For convenience. The drawing area, in pixels.
  
  //Constructor
  public SampleGraphicsWindow(int w, int h) {
    setTitle("My graphics window");
    setSize(w,h);
    wholeWindow = new GraphicsPanel(); //GraphicsPanel is defined below
    add(wholeWindow);
    wholeWindow.addMouseListener(new HandleMouse());
    setVisible(true);
  }//SampleGraphicsWindow constructor
 
  public static void main(String[] args){
    //Simple main program for testing. Just create a window.
    SampleGraphicsWindow test = new SampleGraphicsWindow(700,500);
  }//main
 
  private class GraphicsPanel extends JPanel {
    public void paintComponent(Graphics g){
      /* This is where all the drawing commands will go.
       * Whenever the window needs to be drawn, or redrawn,
       * this method will automatically be called.
       */
     
      //Find out the size of the available area.
      Rectangle r = g.getClipBounds();
      width = r.width;
      height = r.height;
     
      //Just draw two thin diagonal lines. If that works,
      //everything else is easy from there.
      g.drawLine(0,0,width-1,height-1);
      g.drawLine(0,height-1,width-1,0);
      //Look for other methods by searching for "Java Graphics class".
      //You will always use "g." in front of them.
     }//paintComponent method
  }//private inner class graphicsPanel
 
  private class HandleMouse implements MouseListener {
    //The five standard methods are required. I don't want these ones:
    public void mousePressed(MouseEvent e){ /*Do nothing */ }
    public void mouseReleased(MouseEvent e){ /*Do nothing */ }
    public void mouseEntered(MouseEvent e){ /*Do nothing */ }
    public void mouseExited(MouseEvent e){ /*Do nothing */ }
   
    //The only one we really want to pay attention to
    public void mouseClicked(MouseEvent e){
      System.out.println(e.getX()+","+e.getY());
    }//mouseClicked
   
  }//private inner class HandleMouse
 
}//class SampleGraphicsWindow