Getting some errors when trying to run this program, can anyone help.pdf

Getting some errors when trying to run this program, can anyone help fix?
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
/**
* Sudoku program that validates and finds a solution.
* @author
* @
*
*/
public class SudokuSolver extends JFrame implements ActionListener {
/** UID */
private static final long serialVersionUID = 3883151525928534467L;
/** Contains UI for cells */

private SudokuCell[][] sudokuCells;
/** Contains integers representing values in cells. */
private int[][] cellValues;
/**
* Constructor.
* Set up the components and initialize Sudoku.
*/
public SudokuSolver() {
super("Sudoku Solver");
prepareSudokuUI();
// JFrame property
setLayout(new FlowLayout(FlowLayout.CENTER));
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
setLocation((d.width / 2 - 175), (d.height / 2 - 275));
setResizable(false);
setVisible(true);
}
/**
* Set up the UI for application.
*/
private void prepareSudokuUI() {
// Used to align the title, Sudoku grid, and button panels vertically
JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
// Title panel
JPanel title = new JPanel();
title.add(new JLabel(new ImageIcon(getClass().getResource("/resources/title.png"))));
// Sudoku grid panel
JPanel sudokuPanel = new JPanel();

sudokuPanel.setLayout(new GridLayout(3, 3, 1, 1));
// Set up 9 3x3 box panels
JPanel[] boxes = new JPanel[9];
boxes = prepare3x3BoxUI(sudokuPanel, boxes);
// Set up SudokuCells
cellValues = new int[9][9];
sudokuCells = new SudokuCell[9][9];
prepareSudokuCellsUI(boxes);
// Bottom part containing buttons
// First row of buttons
JPanel buttonsPanel = new JPanel();
JButton submitButton = new JButton("Submit"); // Submit to validate the Sudoku
JButton solveButton = new JButton("Solve"); // Solve the Sudoku
JButton eraseButton = new JButton("Erase"); // Clear the cells that are not fixed
JButton eraseAllButton = new JButton("Erase All"); // Clear all cells including fixed ones
buttonsPanel.add(submitButton);
buttonsPanel.add(solveButton);
buttonsPanel.add(eraseButton);
buttonsPanel.add(eraseAllButton);
// Second row of buttons
JPanel buttonsPanel2 = new JPanel();
JButton presetButton = new JButton("Mark As Preset"); // Set filled cells as preset (not
editable)
buttonsPanel2.add(presetButton);
submitButton.addActionListener(this);
solveButton.addActionListener(this);
presetButton.addActionListener(this);
eraseButton.addActionListener(this);
eraseAllButton.addActionListener(this);
panel.add(title);

panel.add(sudokuPanel);
panel.add(buttonsPanel);
panel.add(buttonsPanel2);
add(panel);
}
/**
* Set up 9 3x3 panels for Sudoku panel.
* Use 9 panels to align as 3x3 boxes.
* @param sudokuPanel
* @param boxes 3x3 box panels to be added on Sudoku panel.
* @return instantiated 3x3 box panels.
*/
private JPanel[] prepare3x3BoxUI(JPanel sudokuPanel, JPanel[] boxes) {
for (int i = 0; i < 9; i++) {
boxes[i] = new JPanel();
boxes[i].setLayout(new GridLayout(3, 3, 0, 0));
boxes[i].setBorder(BorderFactory.createMatteBorder(1, 1, 1, 1, Color.BLACK));
sudokuPanel.add(boxes[i]);
}
return boxes;
}
/**
* Set up cells UI(SudokuCell) for input and add them to the panels.
* SudokuCells have to be added to proper panels meaning left-right and top-bottom order
within 3x3 box.
* @param boxes
*/
private void prepareSudokuCellsUI(JPanel[] boxes) {
int index = 0;
// Adjust current row
for (int i = 0; i < 9; i++) {
if (i <= 2)

index = 0;
else if (i <= 5)
index = 3;
else
index = 6;
for (int j = 0; j < 9; j++) {
sudokuCells[i][j] = new SudokuCell(i, j);
boxes[index + (j / 3)].add(sudokuCells[i][j]);
}
}
}
@Override
public void actionPerformed(ActionEvent event) {
JButton button = (JButton) event.getSource();
String buttonType = button.getText();
if (buttonType.equals("Submit"))
submitSudoku();
else if (buttonType.equals("Solve"))
startSolving();
else if (buttonType.equals("Erase"))
erase();
else if (buttonType.equals("Erase All"))
eraseAllIncludingPresetCells();
else
checkPresetCells();
}
/**
* Submit current Sudokue to validate for completeness.
*/
private void submitSudoku() {
if (isSudokuSolved())
JOptionPane.showMessageDialog(getRootPane(),

"Congratulations!
Sudoku has been Completed!",
"Sudoku Validation", JOptionPane.INFORMATION_MESSAGE);
else
"Failed!
Sudoku is not complete!",
"Sudoku Validation", JOptionPane.INFORMATION_MESSAGE);
}
/**
* Start working on the Sudoku if it is ready.
*/
private void startSolving() {
// Don't do anything if Sudoku is already full
if (isSudokuFull()) {
"There are no cells open to start from.",
"Solving Sudoku", JOptionPane.ERROR_MESSAGE);
return;
}
// Validate before starting
if (isValidToStart()) {
markAsPresetCells();
if (!solve(0, 0))
"Unable to solve.",
} else // Don't start solving if Sudoku is not valid at the start
"This is not a valid Sudoku to start.",
}
/**

* Erase all editable cells.
*/
private void erase() {
for (int i = 0; i < 9; i++)
for (int j = 0; j < 9; j++) {
if (cellValues[i][j] != 0) {
if (sudokuCells[i][j].editable) {
sudokuCells[i][j].setText("");
cellValues[i][j] = 0;
}
}
}
}
/**
* Erase all cell values including those with fixed values.
*/
private void eraseAllIncludingPresetCells() {
for (int i = 0; i < 9; i++)
for (int j = 0; j < 9; j++) {
if (cellValues[i][j] != 0) {
if (!sudokuCells[i][j].editable) {
sudokuCells[i][j].editable = true;
sudokuCells[i][j].setEditable(true);
sudokuCells[i][j].setForeground(Color.BLACK);
}
sudokuCells[i][j].setText("");
cellValues[i][j] = 0;
}
}
}
/**
* Evaluate cells before making pre filled cells fixed.
*/
private void checkPresetCells() {

// Validate the current state and make the filled cells fixed
if (!isValidToStart())
"This is not a valid Sudoku to start.",
"Sudoku Solver", JOptionPane.ERROR_MESSAGE);
else
markAsPresetCells();
}
/**
* Check if the Sudoku puzzle is solved correctly.
* @return true if Sudoku is correct.
*/
private boolean isSudokuSolved() {
for (int i = 0; i < 9; i++) {
int[] aRow = new int[9];
int[] aCol = new int[9];
for (int j = 0; j < 9; j++) {
// If this cell is empty, quit because it's not complete
if (cellValues[i][j] == 0)
return false;
aRow[j] = cellValues[i][j];
aCol[j] = cellValues[j][i];
// Check if the value in this cell is duplicated in 3x3 box
if (isContainedIn3x3Box(i, j, cellValues[i][j]))
return false;
}
// Check rows and columns
if (!isRowColumnCorrect(aRow, aCol))
return false;
}

return true;
}
/**
* Check if specified row and column are correct.
* Used when submitting the puzzle.
* @param aRow 9 numbers in a row.
* @param aCol 9 numbers in a column.
* @return true if this row and column are correct.
*/
private boolean isRowColumnCorrect(int[] aRow, int[] aCol) {
Arrays.sort(aRow);
Arrays.sort(aCol);
for (int i = 0; i < 9; i++)
if (aRow[i] != i + 1 && aCol[i] != i + 1)
return false;
return true;
}
/**
* Check if Sudoku is in valid condition to start.
* @return true if Sudoku is ready to start.
*/
private boolean isValidToStart() {
for (int i = 0; i < 9; i++)
for (int j = 0; j < 9; j++)
if (cellValues[i][j] != 0)
if (isContainedIn3x3Box(i, j, cellValues[i][j]) ||
isContainedInRowColumn(i, j, cellValues[i][j]))
return false;
return true;
}

/**
* Make the filled cells fixed.
*/
private void markAsPresetCells() {
for (int i = 0; i < 9; i++)
for (int j = 0; j < 9; j++)
if (cellValues[i][j] != 0)
if (!isContainedIn3x3Box(i, j, cellValues[i][j]) &&
!isContainedInRowColumn(i, j, cellValues[i][j])) {
sudokuCells[i][j].editable = false;
sudokuCells[i][j].setEditable(false);
sudokuCells[i][j].setForeground(new Color(150, 150, 150));
}
}
/**
* Check if a value contains in its 3x3 box for a cell.
* @param row current row index.
* @param col current column index.
* @return true if this cell is incorrect or duplicated in its 3x3 box.
*/
private boolean isContainedIn3x3Box(int row, int col, int value) {
// Find the top left of its 3x3 box to start validating from
int startRow = row / 3 * 3;
int startCol = col / 3 * 3;
// Check within its 3x3 box except its cell
for (int i = startRow; i < startRow + 3; i++)
for (int j = startCol; j < startCol + 3; j++)
if (!(i == row && j == col))
if (cellValues[i][j] == value)
return true;
return false;
}
/**

* Check if a value is contained within its row and column.
* Used when solving the puzzle.
* @param value value in this cell.
* @return true if this value is duplicated in its row and column.
*/
private boolean isContainedInRowColumn(int row, int col, int value) {
for (int i = 0; i < 9; i++) {
// Don't check the same cell
if (i != col)
if (cellValues[row][i] == value)
return true;
if (i != row)
if (cellValues[i][col] == value)
return true;
}
return false;
}
/**
* Check if all cells are filled up.
* @return true if Sudoku is full.
*/
private boolean isSudokuFull() {
for (int i = 0; i < 9; i++)
for (int j = 0; j < 9; j++)
if (cellValues[i][j] == 0)
return false;
return true;
}
/**
* Solve Sudoku recursively.

* @return false if Sudoku is not solved. true if Sudoku is solved.
*/
private boolean solve(int row, int col) {
// If it has passed through all cells, start quitting
if (row == 9)
return true;
// If this cell is already set(fixed), skip to the next cell
if (cellValues[row][col] != 0) {
if (solve(col == 8? (row + 1): row, (col + 1) % 9))
return true;
} else {
// Random numbers 1 - 9
Integer[] randoms = generateRandomNumbers();
for (int i = 0; i < 9; i++) {
// If no duplicates in this row, column, 3x3, assign the value and go to the next
if (!isContainedInRowColumn(row, col, randoms[i]) &&
!isContainedIn3x3Box(row, col, randoms[i])) {
cellValues[row][col] = randoms[i];
sudokuCells[row][col].setText(String.valueOf(randoms[i]));
// Move to the next cell left-to-right and top-to-bottom
if (solve(col == 8? (row + 1) : row, (col + 1) % 9))
return true;
else {
// Initialize the cell when backtracking (case when the value in the next cell was
not valid)
cellValues[row][col] = 0;
sudokuCells[row][col].setText("");
}
}
}
}

return false;
}
/**
* Generate 9 unique random numbers.
* @return array containing 9 random unique numbers.
*/
private Integer[] generateRandomNumbers() {
ArrayList randoms = new ArrayList();
for (int i = 0; i < 9; i++)
randoms.add(i + 1);
Collections.shuffle(randoms);
return randoms.toArray(new Integer[9]);
}
/**
* A SudokuCell represents a cell for input.
*
*
*/
private class SudokuCell extends JTextField {
/** UID */
private static final long serialVersionUID = 4690751052748480438L;
/** Determine if this cell can accept input. */
private boolean editable;
/**
* Constructor
* @param row index for row of this cell.
* @param col index for column of this cell.
*/
public SudokuCell(final int row, final int col) {
super(1);

editable = true;
setBackground(Color.WHITE);
setBorder(BorderFactory.createLineBorder(Color.GRAY));
setHorizontalAlignment(CENTER);
setPreferredSize(new Dimension(35, 35));
setFont(new Font("Lucida Console", Font.BOLD, 28));
addFocusListener(new FocusListener(){
@Override
public void focusGained(FocusEvent arg0) {
// Change colors of fields located in vertical, horizontal, and 3x3 fields
for (int i = 0; i < 9; i++) {
// Horizontal
sudokuCells[i][col].setBackground(new Color(255, 227, 209));
// Vertical
sudokuCells[row][i].setBackground(new Color(255, 227, 209));
}
// 3x3 box
sudokuCells[i][j].setBackground(new Color(255, 227, 209));
}
@Override
public void focusLost(FocusEvent arg0) {
// Set the previous color of fields back to white
// Reset focus (set background color back to white)
for (int i = 0; i < 9; i++) {
// Horizontal
sudokuCells[i][col].setBackground(Color.WHITE);
// Vertical

sudokuCells[row][i].setBackground(Color.WHITE);
}
// 3x3 box
sudokuCells[i][j].setBackground(Color.WHITE);
}
});
addKeyListener(new KeyAdapter() {
@Override
public void keyPressed(KeyEvent e) {
// Only allow numeric input
if (editable)
if (e.getKeyChar() >= '1' && e.getKeyChar() <= '9') {
setEditable(true);
setText(""); // Keep it 1 letter
cellValues[row][col] = e.getKeyChar() - 48;
} else if (e.getKeyCode() == KeyEvent.VK_BACK_SPACE) {
setEditable(true);
setText("0"); // Avoid beep sound
cellValues[row][col] = 0;
} else
setEditable(false);
// Navigation by arrow keys
switch (e.getKeyCode()) {
case KeyEvent.VK_DOWN:
sudokuCells[(row + 1) % 9][col].requestFocusInWindow();
break;
case KeyEvent.VK_RIGHT:
sudokuCells[row][(col + 1) % 9].requestFocusInWindow();
break;

case KeyEvent.VK_UP:
sudokuCells[(row == 0)? 8 : (row - 1)][col].requestFocusInWindow();
break;
case KeyEvent.VK_LEFT:
sudokuCells[row][(col == 0)? 8 : (col - 1)].requestFocusInWindow();
break;
}
}
});
}
}
/**
* @param args
*/
public static void main(String[] args) {
new SudokuSolver();
}
}
Solution
Hi,
When i just copied the code above to eclipse and tried running this is the error i get:
Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.(ImageIcon.java:205)
at SudokuSolver.prepareSudokuUI(SudokuSolver.java:67)
at SudokuSolver.(SudokuSolver.java:45)
at SudokuSolver.main(SudokuSolver.java:550)
That is the only error i got
And the reason for the error is
title.add(new JLabel(new ImageIcon(getClass().getResource("/resources/title.png")))); this
perticular line in private void prepareSudokuUI() function. we should give a image file to the
program so give a correct path where you have copied the image file.
my suggestion is that u keep a image file in the same folder where you have this perticular .java
file and just replace the path with image file name

name. title.add(new JLabel(new ImageIcon(getClass().getResource("myimage.png")))); That
will work :)
if you are getting any other error you should specify in the question. Anyfurther clarification
needed comment below.

Getting some errors when trying to run this program, can anyone help.pdf

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