I need help debugging this code. I need to convert the 2d array into an int or a string then into an int

package sudokusolver;

import java.util.*; import java.io.*;

public class SudokuSolver { // constants // the width (and height) of the whole puzzle private final int PUZZLE_WIDTH; // the dimensions of the inner boxes private final int SUB_WIDTH, SUB_HEIGHT; // variables // the board of cells public String[][] board; public SudokuSolver(int puzzleWidth, int subWidth, int subHeight) throws IllegalDimensionException { if(puzzleWidth <= 0 || subWidth <= 0 || subHeight <= 0 || subWidth * subHeight != puzzleWidth) throw new IllegalDimensionException(); PUZZLE_WIDTH = puzzleWidth; SUB_WIDTH = subWidth; SUB_HEIGHT = subHeight; }

public void loadBoard(){ String [][]board = { {3,0,0,0,0,0,2,5,0}, {1,0,0,9,0,5,0,0,8}, {0,0,4,0,7,6,0,0,0}, {0,0,0,0,0,0,0,0,4}, {8,0,6,3,0,9,0,0,7}, {0,0,9,0,2,1,6,0,0}, {0,7,0,4,0,2,8,0,0}, {0,5,0,0,8,0,1,0,0}, {0,0,0,0,0,0,0,6,9} };

String x = board; // read each number for(int r = 0; r != board.length; ++r) { for(int c = 0; c != board[r].length; ++c) { // ensure there is another number // ensure the value is valid //////////////read from file if(x < 0 || x > board.length) throw new FileFormatException(); // ensure the value can be placed in the cell ///////////read from file if(x != 0 && !canPlace(r, c, x)) throw new IllegalPuzzleException(); board[r][c] = x; } // consume the blank line at the end of the row (if the loop is not on the last row) and ensure the puzzle dimensions are correct if(r != board.length - 1) throw new FileFormatException(); } } /** * Determines if x can be placed in the r'th row and c'th column. * * Pre-Conditions: r and c must be greater than or equal to zero and less than the puzzle width. * x must be greater than 0 and less than or equal to the puzzle width. * The board must be initialized. * Post-Condition: true is returned if x can be placed at (r, c), false is returned otherwise. * Responses: Throws an exception if r or c are invalid. * Returns an erroneous result if x is invalid. * Throws an exception if the board is uninitialized. * * @param r The row that will be checked. * @param c The column that will be checked. * @param x The value that will be searched for. * @return true if x can be placed at (r, c), false otherwise. */ private boolean canPlace(int r, int c, int x) { if(r < 0 || c < 0 || r >= PUZZLE_WIDTH || c >= PUZZLE_WIDTH || x <= 0 || x > PUZZLE_WIDTH) throw new IllegalArgumentException(); return canPlaceInRow(r, x) && canPlaceInCol(c, x) && canPlaceInSubBox(r, c, x); } /** * Determines if x can be placed in the r'th row. * * Pre-Conditions: r must be greater than or equal to zero and less than the puzzle width. * x must be greater than 0 and less than or equal to the puzzle width. * The board must be initialized. * Post-Condition: true is returned if x can be placed in the r'th row, false is returned otherwise. * Responses: Throws an exception if r is invalid. * Returns an erroneous result if x is invalid. * Throws an exception if the board is uninitialized. * * @param r The row that will be checked. * @param x The value that will be searched for. * @return true if x can be placed in the r'th row, false otherwise. */ private boolean canPlaceInRow(int r, int x) { if(r < 0 || r >= PUZZLE_WIDTH || x <= 0 || x > PUZZLE_WIDTH) throw new IllegalArgumentException(); for(int value : board[r]) if(value == x) return false; return true; } /** * Determines if x can be placed in the c'th column. * * Pre-Conditions: c must be greater than or equal to zero and less than the puzzle width. * x must be greater than 0 and less than or equal to the puzzle width. * The board must be initialized. * Post-Condition: true is returned if x can be placed in the c'th column, false is returned otherwise. * Responses: Throws an exception if c is invalid. * Returns an erroneous result if x is invalid. * Throws an exception if the board is uninitialized. * * @param c The column that will be checked. * @param x The value that will be searched for. * @return true if x can be placed in the c'th column, false otherwise. */ private boolean canPlaceInCol(int c, int x) { if(c < 0 || c >= PUZZLE_WIDTH || x <= 0 || x > PUZZLE_WIDTH) throw new IllegalArgumentException(); for(int r = 0; r != board.length; ++r) if(board[r][c] == x) return false; return true; } /** * Determines if x can be placed in the sub-box that contains the (r, c) cell. * * Pre-Conditions: r and c must be greater than or equal to zero and less than the puzzle width. * x must be greater than 0 and less than or equal to the puzzle width. * The board must be initialized. * Post-Condition: true is returned if x can be placed in the sub-box that contains the (r, c) cell, * false is returned otherwise. * Responses: Throws an exception if r or c are invalid. * Returns an erroneous result if x is invalid. * Throws an exception if the board is uninitialized. * * @param r The row of the cell to be checked. * @param c The column of the cell to be checked. * @param x The value that will be searched for. * @return true if x can be placed in the sub-box that contains the (r, c) cell, false otherwise. */ private boolean canPlaceInSubBox(int r, int c, int x) { if(r < 0 || c < 0 || r >= PUZZLE_WIDTH || c >= PUZZLE_WIDTH || x <= 0 || x > PUZZLE_WIDTH) throw new IllegalArgumentException(); // determine the "clip" rows and columns for the sub-box to be searched // round down to the nearest leftmost cell of a sub-box int leftCol = (c / SUB_WIDTH) * SUB_WIDTH; int rightCol = leftCol + SUB_WIDTH - 1; // round down to the nearest topmost cell of a sub-box int topRow = (r / SUB_HEIGHT) * SUB_HEIGHT; int bottomRow = topRow + SUB_HEIGHT - 1; // search the sub-box for the value for(int searchR = topRow; searchR <= bottomRow; ++searchR) for(int searchC = leftCol; searchC <= rightCol; ++searchC) if(board[searchR][searchC] == x) return false; return true; } /** * Prints the board to the screen. * * Pre-Conditions: The board must be initialized. * Post-Conditions: The board is printed to the screen. * Responses: Throws an exception if the board is uninitialized. */ public void printBoard() { for(int i = 0; i != board.length; ++i) { System.out.print(" --"); if((i + 1) % SUB_WIDTH == 0) System.out.print(" "); } System.out.println(); for(int row = 0; row < PUZZLE_WIDTH; ++row) { for(int col = 0; col < PUZZLE_WIDTH; ++col) { int value = board[row][col]; String out = "|" + (col % SUB_WIDTH == 0 && col != 0 ? "|" : ""); if(value == 0) out += " "; else { out += value + (value < 10 ? " " : ""); } System.out.print(out); } System.out.println("|"); if((row + 1) % SUB_HEIGHT == 0) { for(int i = 0; i != board.length; ++i) { System.out.print(" --"); if((i + 1) % SUB_WIDTH == 0) System.out.print(" "); } System.out.println(); } } System.out.println(); } /** * Determines the row of the cell that follows the (r, c) cell. * * Pre-Conditions: r and c must be greater than or equal to zero and less than the puzzle width. * (r, c) must not be the last cell in the board. * Post-Condition: r + 1 is returned if (r, c) is the last cell in the row, r is returned otherwise. * Responses: Throws an exception if r or c is invalid. * Returns an erroneous result if (r, c) is the last cell in the board. * * @param r The row of the cell. * @param c The column of the cell. * @return r + 1 if (r, c) is the last cell in the row, r otherwise. */ private int getNextRow(int r, int c) { if(r < 0 || c < 0 || r >= PUZZLE_WIDTH || c >= PUZZLE_WIDTH) throw new IllegalArgumentException(); return (c == PUZZLE_WIDTH - 1 ? r + 1 : r); } /** * Determines the column of the cell that follows the (r, c) cell. * * Pre-Conditions: r and c must be greater than or equal to zero and less than the puzzle width. * (r, c) must not be the last cell in the board. * Post-Condition: 0 is returned if (r, c) is the last cell in the row, c + 1 is returned otherwise. * Responses: Throws an exception if r or c is invalid. * Returns an erroneous result if (r, c) is the last cell in the board. * * @param r The row of the cell. * @param c The column of the cell. * @return 0 if (r, c) is the last cell in the row, c + 1 otherwise. */ private int getNextCol(int r, int c) { if(r < 0 || c < 0 || r >= PUZZLE_WIDTH || c >= PUZZLE_WIDTH) throw new IllegalArgumentException(); return (c == PUZZLE_WIDTH - 1 ? 0 : c + 1); } /** * Determines if the (r, c) cell is the last cell in the board; in other words, (r, c) is the bottom right cell. * * Pre-Conditions: r and c must be greater than or equal to zero and less than the puzzle width. * Post-Condition: true is returned if the (r, c) cell is the last cell in the board, false is returned otherwise. * Responses: Throws an exception if r or c is invalid. * * @param r The row of the cell. * @param c The column of the cell. * @return true if the (r, c) cell is the last cell in the board, false otherwise. */ private boolean isLastCell(int r, int c) { return r == PUZZLE_WIDTH - 1 && c == PUZZLE_WIDTH - 1; } /** * Attempts to solve for the value of the (r, c) cell. (This is a helper method for solvePuzzle()). * * Pre-Conditions: r and c must be greater than or equal to zero and less than the puzzle width. * The cell must NOT already contain a value (besides 0). * Post-Conditions: Cell (r, c) and all following cells will contain the correct value and true will be returned if the previous cells are * all correct (and a solution exists). This indicates that the puzzle is solved. * Cell (r, c) will contain 0 and false will be returned if any previous values are incorrect. * Responses: Throws an exception if r or c is invalid, or if the board is uninitialized. * Overwrites the old value at (r, c) if an old value exists. * * @param r The row of the cell being solved * @param c The column of the cell being solved. * @return true if the previous cells are all correct (and a solution exists), false otherwise. */ private boolean solveCell(int r, int c) { if(r < 0 || c < 0 || r >= PUZZLE_WIDTH || c >= PUZZLE_WIDTH) throw new IllegalArgumentException(); for(int guess = 1; guess <= PUZZLE_WIDTH; ++guess) { // if the guess can be placed at (r, c) if(canPlace(r, c, guess)) { // try it board[r][c] = guess; // check for base case (finished) if(isLastCell(r, c)) return true; // otherwise, keep going if(solvePuzzle(getNextRow(r, c), getNextCol(r, c))) return true; // if the puzzle could not be solved, try a new guess } } // if all the guesses have been tried and none worked, erase the last guess board[r][c] = 0; return false; // backtrack } /** * Solves the puzzle, starting at cell (r, c). * * Pre-Conditions: r and c must be greater than or equal to zero and less than the puzzle width. * Post-Conditions: Cell (r, c) and all following cells will contain the correct value and true will be returned if the previous cells are * all correct (and a solution exists). This indicates that the puzzle is solved. * Cell (r, c) will contain 0 or its old value, and false will be returned if any previous values are incorrect. * Responses: Throws an exception if r or c is invalid, or if the board is uninitialized. * * @param r The row of the cell being solved * @param c The column of the cell being solved. * @return true if the previous cells are all correct (and a solution exists), false otherwise. */ public boolean solvePuzzle(int r, int c) { if(r < 0 || c < 0 || r >= PUZZLE_WIDTH || c >= PUZZLE_WIDTH) throw new IllegalArgumentException(); // check if the cell already has a value if(board[r][c] != 0) { // check if this is the last spot if(isLastCell(r, c)) return true; // puzzle is solved // otherwise, go to the next cell WITHOUT overwriting this value if(solvePuzzle(getNextRow(r, c), getNextCol(r, c))) return true; // the puzzle is solved // if the puzzle could not be solved, backtrack without overwriting this value return false; } // if the cell does not have a value, try all possible guesses return solveCell(r, c); } public static void main(String[] args) { // prompt for the puzzle dimensions int puzzleWidth, subWidth, subHeight; System.out.print("Enter the width of the entire puzzle: "); puzzleWidth = 9; System.out.print("Enter the width of the sub-boxes. For example, a 9x9 puzzle has sub-boxes of width 3: "); subWidth =3; System.out.print("Enter the height of the sub-boxes: "); subHeight =3; // create the solver SudokuSolver solver = new SudokuSolver(puzzleWidth, subWidth, subHeight); // prompt for a file System.out.print("Enter the file containing a puzzle: "); solver.loadBoard(); // print the initial puzzle System.out.println("This is the initial puzzle: "); solver.printBoard(); System.out.println(" Now solving the puzzle..."); long start = System.nanoTime(); if(solver.solvePuzzle(0, 0)) { System.out.println("The puzzle has been solved in " + (System.nanoTime() - start) / 1000000d + "ms "); solver.printBoard(); } else { System.out.println("The puzzle has no solution."); } }; // end main } // end class

// Named exceptions for the above methods

// Exception thrown if supplied dimensions to the SudokuSolver do not form a valid puzzle. class IllegalDimensionException extends Exception { /** * Default. */ private static final long serialVersionUID = 1L; }

// Exception thrown if a file's sudoku puzzle's format is invalid, or if it's size does not // match the supplied constants class FileFormatException extends Exception { /** * Default. */ private static final long serialVersionUID = 1L; }

// Exception thrown if a file's puzzle is in an invalid state. For example, if the file contains // two 1's in the same column, this exception is thrown. class IllegalPuzzleException extends Exception { /** * Default. */ private static final long serialVersionUID = 1L; }