The Art & Science of Java Chapter 4 Exercise 14 Checkers

[M Ford]

Hi guys

I'm going through CS106A(Programming Methodology) course from iTunes where in the The Art & Science of Java book associated with the course, there is an exercise called Checkers.

Below is that exercise and as you can see, I've completed the program but not as polished as I hope.

I am using Eclipse and had no Programming Knowledge prior to this course.

/*
 * File: CheckerBoard2.java
 * -----------------------
 * This is an extension to the CheckerBoard program. It is an enhancement to the original
 * so that it centers the checkerboard horizontally and draws the set of red and black checkers
 * corresponding to the initial state of the game. The other change is that the color of the
 * dark squares has been changed from black to grey so that the checkers are not lost against
 * the background.
 *
 *
 */

import java.awt.Color;

import acm.program.*;
import acm.graphics.*;

public class CheckerBoard2 extends GraphicsProgram{
   
     public void run(){
         
//This is for the checkerboard//
         
         double sqSize = (double) getHeight() / N_Rows;
         double figWidth = N_Columns * sqSize;
         
         for (int i = 0; i < N_Rows; i++) { 
        	 for (int j = 0; j < N_Columns; j++) { 
                 double x = (j * sqSize) + (getWidth() / 2 - figWidth / 2); 
                 double y = i * sqSize;           
                 	GRect sq = new GRect(x, y, sqSize, sqSize); 
                 	sq.setFilled((i+j) % 2 != 0); 
                 	sq.setFillColor(Color.gray); 
                 	add(sq);
                 

//This is for the red checkers       
                   
                   
                  
                    for (int l = 0; l < 3; l++) { 
                    	for (int m = 0; m < N_Columns; m++) { 
                            double p = (m * sqSize) + (getWidth() / 2 - figWidth / 2); 
                            double s = (l * sqSize) + (getHeight() / 2 - figWidth/ 2); 
                               GOval ov = new GOval(p, s, sqSize, sqSize); 
                               ov.setFilled((l+m) % 2 != 0);
                               ov.setFillColor(Color.RED); 
                               add(ov); 
                        } 
                    } 
                 
//This is for the black checkers 
                   
                    for (int n = 5; n < N_Rows; n++) { 
                    	for (int o = 0; o < N_Columns; o++) { 
                            double t = (o * sqSize) + (getWidth() / 2 - figWidth / 2); 
                            double a = (n * sqSize) + (getHeight() / 2 - figWidth/ 2);
                            GOval ovl = new GOval(t, a, sqSize, sqSize); 
                            ovl.setFilled((n+o) % 2 != 0);
                            ovl.setFillColor(Color.BLACK); 
                            add(ovl);
                   
                        }
                    }
              }
        }
  }
 
/*Private constants*/
  private static final double N_Rows=8;
 
 
/*Private constants*/
        private static final double N_Columns=8;


}

-------------------------------------

How do get rid of the circles or blank checkers from the white squares?

Also how do I make the checkers smaller and centred in each black squares?

Thank you guys.

[Campbell Ritchie]

Why are you using doubles for the number of rows? That is definitely an integer number. Why have you got N_Rows (which should be spelt in UPPER_CASE throughout) and columns as well? The board is square, so you always have rows and columns the same.
How are you drawing the board? Are you using the paintComponent method? In which case you would call super.paintComponent(g); as the first line of that method.
Why have you got all that GUI work in the run() method? That ought to be in the constructor of the GUI class, or a method called private void initGUI() called from the constructor.

Don’t know exactly why you are getting that problem, but check those queries and see how far you get.

[Goran Dragutinovic]

The proper code is:

import acm.graphics.*;
import acm.program.*;
import java.awt.*;

public class Chapter4 extends GraphicsProgram {
	
	int sqSize = getHeight() / N_ROWS;
	int figWidth = (getWidth()/2) -(N_COLUMNS * sqSize)*(N_ROWS*sqSize);
	
	//this is for the checkboard 
	
	public void run() {
	   int sqSize = getHeight() / N_ROWS;
       for (int i = 0; i < N_ROWS; i++) {
       	for (int j = 0; j < N_COLUMNS; j++) {
       		int x = (j * sqSize) + (getWidth()) / 2 - (figWidth / 2);
       		int y = i * sqSize;
       	    
       		GRect sq = new GRect (x, y, sqSize, sqSize);
       		sq.setFilled((i + j) % 2 != 0);
       		sq.setColor(Color.GRAY);
       		add(sq);
       	}
       	//for red checkers
       	for (int q = 0; q < 3; q++) { 
       		for (int z = 0; z < N_COLUMNS; z++) { 
       		int s = (z * sqSize) + (getWidth() / 2 - figWidth / 2); 
       		int t = (q * sqSize); 
       		GOval red = new GOval(s, t, sqSize, sqSize); 
       			if ((q+z) % 2 != 0) { 
       			red.setFilled(true);
       			red.setFillColor(Color.RED); 
       			add(red); 
       		}
		// for black checkers
       			for (int a = 5; a < N_ROWS; a++) { 
       	       		for (int b = 0; b < N_COLUMNS; b++) { 
       	       		int c = (b * sqSize) + (getWidth() / 2 - figWidth / 2); 
       	       		int d = (a * sqSize);
       	       		GOval black = new GOval(c, d, sqSize, sqSize); 
       	       			if ((a+b) % 2 != 0) { 
       	       			black.setFilled(true);
       	       			black.setFillColor(Color.BLACK); 
       	       			add(black); 
       		}
       		}
   			}
       		}
       	}
   }
}
	
	//private constants
	
	private static final int N_ROWS = 8;
	private static final int N_COLUMNS = 8;
}

[Jeremy Mazz]

I have a question regarding this line

int figWidth = (getWidth()/2) -(N_COLUMNS * sqSize)*(N_ROWS*sqSize);  

I tried running this code in Eclipse and I ran a println on this statement and received '0' as its output. I know this can't be correct. What is this variable supposed to be calculating. The code above doesn't have any comments. Thanks.

[Tony Docherty]

Jeremy Mazz wrote:I have a question regarding this line

int figWidth = (getWidth()/2) -(N_COLUMNS * sqSize)*(N_ROWS*sqSize);  

I tried running this code in Eclipse and I ran a println on this statement and received '0' as its output. I know this can't be correct. What is this variable supposed to be calculating. The code above doesn't have any comments. Thanks.

Welcome to the Ranch.

To be honest I don't know. Looking at how it is used I guess it's supposed to be the total board width and the OP was assuming the panel was going to be wider than it was high and so the board would fill the height but would need to be centered on the width. Having said that the calculation doesn't appear to be calculating that so maybe I'm barking up the wrong tree. Without having the rest of the code so I can run it, it's hard to give further advice, sorry.

Maybe someone else here knows the question and can give a better answer.

[Jeremy Mazz]

Thanks for replying, the rest of the code is two posts up from my original post. I was referring to Goran Dragutinovic code.

[K. Tsang]

Jeremy Mazz wrote:Thanks for replying, the rest of the code is two posts up from my original post. I was referring to Goran Dragutinovic code.

I figure that line puts the checker board in the center of the panel. hence the "getWidth()/2 -" part.

[Tony Docherty]

Jeremy Mazz wrote:Thanks for replying, the rest of the code is two posts up from my original post. I was referring to Goran Dragutinovic code.

Yes, I saw that. That's how I worked out it was probably being used to center the panel along the X axis. But that code is not an SSCCE and so can't be run.