Looking for help.

[Shawn Gordian]

I've been stuck trying to figure out whats going wrong for a few hours. Program isnt giving me desired output and I cant tell what I'm doing wrong.

What it should be doing:
Accept a starting point from the user. Then try to complete the knights tour. Mark each stop on the board and then the piece is not allowed to use that spot again. An attempt to move off the 8x8 grid isnt allowed.
I have to use the board class given to me.

What its doing. Accepts the user input and some times it'll do a move or two, but some times it will not compile.

package runknightstour;

/**
 *
 * @author Anita
 */
public class RunKnightsTour {

   public static void main(String[] args) {
    
      KnightMoves tour = new KnightMoves();
      /* tour.getStartPosition(); */
      tour.runTour();

    }

}

package runknightstour;
import java.util.Random;
import java.util.Scanner;

public class KnightMoves 
{
    public final int COMPLETE_TOUR = 64;
    private ChessBoard kBoard = new ChessBoard();
    private int[][] moves = new int[8][2];
    private int stepNumber;
    private int currentRow;
    private int currentCol;
    private int startRow;
    private int startCol;
    
    
    public KnightMoves()
    {
        moves[0][0] = -2; // move 0 row offset
        moves[0][1] = 1; // move 0 col offset
        
        moves[1][0] = -1; // move 1 row offset
        moves[1][1] = 2; // move 1 col offset
        
        moves[2][0] = 1; // move 2 row offset
        moves[2][1] = 2; // move 2 col offset
        
        moves[3][0] = 2; // move 3 row offset
        moves[3][1] = 1; // move 3 col offset
        
        moves[4][0] = 2; // move 4 row offset
        moves[4][1] = -1; // move 4 col offset
        
        moves[5][0] = 1; // move 5 row offset
        moves[5][1] = -2; // move 5 col offset
        
        moves[6][0] = -1; // move 6 row offset
        moves[6][1] = -2; // move 6 col offset
        
        moves[7][0] = -2; // move 7 row offset
        moves[7][1] = -1; // move 7 col offset
        
        stepNumber = 0;
        startRow = startCol = 1;
        currentRow = currentCol = 1;  
    }
    /**
     *  Description:  Get the starting board Position (row, col) for the 
     *                KNIGHT from program user
     */
    public void getStartPosition()
    {
        Scanner input = new Scanner(System.in);
        System.out.print("\n enter a starting location for the knight's row ");
        startRow = input.nextInt();
        System.out.print("\n enter a starting location for the knight's col ");
        startCol = input.nextInt();
        
        kBoard.setSquare(startRow, startCol, 1);
        
        System.out.println(kBoard);
   }
   /**
    * Mutator: runTour()
    */
    public void runTour()
    {
        getStartPosition();
        // while stepNumber < 64 and takeStep() == true
        // knight should keep stepping
        // if stepNumber is equal to COMPLETE_TOUR
        // report that the knight made a complete tour
       while (stepNumber < 64 && takeStep() == true )
                {   
                    
                    if (stepNumber == COMPLETE_TOUR)
                    {
                        System.out.println("To Complete Successfully");
                    }
                }
        
        
        System.out.println(this);
        
    }
   
   
    private boolean takeStep()
    {   boolean step = false;
        
        Random rand = new Random();
        int random1;
        int attempts =0;
        random1 = rand.nextInt(8);
        int tryStepRow =0;
        int tryStepCol=0;
        do {
               tryStepRow = currentRow + moves[random1][0];
               tryStepCol = currentCol + moves[random1][1];
                
               if(kBoard.getSquare(tryStepRow,tryStepCol)==0)
               {
                   kBoard.setSquare(tryStepRow,tryStepCol, stepNumber++);
                           currentRow= tryStepRow;
                           currentCol = tryStepCol;
                           
                          
               }
               else {
                  attempts++;
               }
               
               } while (step == false && attempts < 200);
          
           return step;
    }
     public String toString()
    {
       String whatHappened = "";
        whatHappened += "Starting location: [" + startRow + ", "
          + startCol + "]\n";
        whatHappened += " Tour ended after " + stepNumber + " steps\n";
        whatHappened += "The knight got stuck in location ["
          + (currentRow - 1) + ", " + (currentCol - 1) + "]\n";
        return whatHappened;
        
    } 
    
}

package runknightstour;


public class ChessBoard {
   public final int ROWS = 8;
   public final int COLS = 8;
   public final int FRAMESIZE = 12;
   private int[][] board = new int[FRAMESIZE][FRAMESIZE];
  
    public ChessBoard()
    {
       for (int y = 0; y < board.length; y++) {

          for (int x = 0; x < board[y].length; x++) {

             board[y][x] = -1;

          }
          for (int r = 2; r < ROWS + 2; r++)        {
           for (int c = 2; c < COLS + 2; c++)            {
                board[r][c] = 0;
            }
        } 

       

       

       }
    }
    public String toString()
    {
       String output = "";
       for (int r = 0; r < FRAMESIZE; r++)        {
           for (int c = 0; c < FRAMESIZE; c++)            {
                output += board[r][c];   
                output += "\t";
            }
            output += "\n\n";
        }
       return output; 
    }
      /**
       * 
       * @param row
       * @param col
       * @param inStep in the range of 1 - 64
       */      
    public void setSquare(int row, int col, int inStep)
    {
        //  adjust input to match 2 - 9
        row += 1;
        col +=1;
        if (row > 1 && row < 10 && col > 1 && col < 10)
        {
            board[row][col] = inStep;
        }
    }
    public int getSquare (int row, int col)
    {
        return board[row][col];
    }
    
    
    
}

[Junilu Lacar]

First, you have to get some terms straight. Your statement that your program will do a move or two but doesn't "compile" sometimes is inaccurate. A program must first compile successfully before you can run it. No exceptions. So you probably meant to say that your program fails with an exception sometimes.

I can see at least a couple of problems with your code. First, you have a variable, step, that you initialize to false but never set to true. Yet, your loop condition includes a check on step. When it comes to checking a Boolean value, don't compare the variable to true or false. This is not only redundant, it is also error prone because it's easy to miss a character and write step = false instead of step == false. It's redundant because the variable itself is already sufficient as a Boolean expression. Comparing it to true or false is like asking, "Did you make a step, yes or no?" The "yes or no" part of the question is redundant. Using a variable name that gives more of a sense of yes/no will help you avoid things like this. For example, if you use stepTaken instead, your code would read more naturally:

while (!stepTaken && ...)

This reads as "while not stepTaken and ..."

The more serious problem you have in that code is that it's possible to step out of bounds of the board. If you try to do that, you'll get an IndexOutOfBoundsException. You need to perform some checks to ensure that your indices are valid before you try to use them on your board.

[Junilu Lacar]

Also, your program is difficult to read because you haven't aligned everything properly. Indent your code properly so that you can clearly tell where each block of statements (if, while-loop, for-loop, method, class, etc.) begins and ends. Imagine your mailbox being in front of your neighbor's house three houses away from yours. That would be confusing for the mailman delivering your mail, right? You're liable to get your mail misdirected. Improperly indented code is like that to people reading your code. They can't easily tell which statements logically go with each other.

Other languages like Python actually require you to indent your code properly in order for the program to behave correctly. Java, however, doesn't care about indentation. Indentation is for the human reader's benefit. So, indent your programs properly for the benefit of its human readers, including yourself.

Refer to the following for guidelines:
http://www.javaranch.com/styleLong.jsp
http://www.oracle.com/technetwork/java/javase/documentation/codeconventions-136091.html

If you are using an IDE like Eclipse, you can have it format your code for you. Just press Ctrl+Shift+F or Cmd+Shift+F (on Mac).