Game of Life Animation Java

Question

I have this Board class:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.Timer;
public class Board extends JPanel implements ActionListener {
 Timer timer = new Timer(500, this);
 private static boolean[][] emptyBoard = {{false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false},
 {false, false, false, false, false, false, false, false, false, false}};
 private boolean[][] board;
 private boolean isActive = false;
 private int height;
 private int width;
 private int multiplier = 55;
 private JButton button1;
 private JButton button2;
 private JButton button3;
 public Board() {
 this(emptyBoard);
 }
 public Board(final boolean[][] board) {
 this.board = board;
 height = board.length;
 width = board[0].length;
 setBackground(Color.black);
 button1 = new JButton("Run");
 add(button1);
 button1.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 isActive = !isActive;
 button1.setText(isActive ? "Pause" : "Run");
 }
 });
 button2 = new JButton("Random");
 add(button2);
 button2.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 setBoard(randomBoard());
 }
 });
 button3 = new JButton("Clear");
 add(button3);
 button3.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 setBoard(clearBoard());
 }
 });
 addMouseListener(new MouseListener() {
 @Override
 public void mouseClicked(MouseEvent e) {
 }
 @Override
 public void mouseEntered(MouseEvent e) {
 }
 @Override
 public void mouseExited(MouseEvent e) { 
 }
 @Override
 public void mousePressed(MouseEvent e) {
 getBoard()[e.getY() / multiplier][e.getX() / multiplier] = !getBoard()[e.getY() / multiplier][e.getX() / multiplier];
 }
 @Override
 public void mouseReleased(MouseEvent e) { 
 }
 });
 timer.start();
 }
 public int getMultiplier() {
 return multiplier;
 }
 public boolean[][] getBoard() {
 return board;
 }
 public void setBoard(boolean[][] boardToSet) {
 for (int i = 0; i < height; i++) {
 for (int j = 0; j < width; j++) {
 board[i][j] = boardToSet[i][j];
 }
 }
 }
 @Override
 public void paintComponent(Graphics g) {
 super.paintComponent(g);
 for (int i = 0; i < height; i++) {
 for (int j = 0; j < width; j++) {
 g.setColor(board[i][j] ? Color.green : Color.gray);
 g.fillRect(j * multiplier, i * multiplier, multiplier - 1, multiplier - 1);
 }
 }
 if (isActive) {
 timer.start();
 }
 else {
 timer.stop();
 repaint();
 }
 }
 public void actionPerformed(ActionEvent e) {
 board = nextGeneration();
 repaint();
 }
 public boolean[][] randomBoard() {
 Random rand = new Random();
 boolean[][] randBoard = new boolean[height][width];
 for (int i = 0; i < height; i++) {
 for (int j = 0; j < width; j++) {
 randBoard[i][j] = rand.nextBoolean();
 }
 }
 return randBoard;
 }
 public boolean[][] clearBoard() {
 boolean[][] emptyBoard = new boolean[height][width];
 for (int i = 0; i < height; i++) {
 for (int j = 0; j < width; j++) {
 emptyBoard[i][j] = false;
 }
 }
 return emptyBoard;
 }
 public int countSurrounding(int a, int b) {
 int count = 0;
 int[][] surrounding = {{a - 1, b - 1},
 {a - 1, b },
 {a - 1, b + 1},
 {a , b - 1},
 {a , b + 1},
 {a + 1, b - 1},
 {a + 1, b },
 {a + 1, b + 1}};
 for (int[] i: surrounding) {
 try {
 if (board[i[0]][i[1]]) {
 count++;
 }
 }
 catch (ArrayIndexOutOfBoundsException e) {}
 }
 return count;
 }
 public boolean[][] nextGeneration() {
 boolean[][] nextBoard = new boolean[height][width];
 for (int i = 0; i < height; i++) {
 for (int j = 0; j < width; j++) {
 nextBoard[i][j] = board[i][j];
 }
 }
 for (int i = 0; i < height; i++) {
 for (int j = 0; j < width; j++) {
 if (board[i][j] && !(countSurrounding(i, j) == 2 || countSurrounding(i, j) == 3)) {
 nextBoard[i][j] = false;
 }
 else if (!board[i][j] && countSurrounding(i, j) == 3) {
 nextBoard[i][j] = true;
 }
 }
 }
 return nextBoard;
 } 
}

and this GameOfLife class:

import javax.swing.JFrame;
class GameOfLife {
 public static void main(String[] args) {
 Board boardPanel = new Board();
 JFrame frame1 = new JFrame();
 frame1.setTitle("The Game of Life");
 frame1.setSize(boardPanel.getBoard()[0].length * boardPanel.getMultiplier() + 5, boardPanel.getBoard().length * boardPanel.getMultiplier() + 27);
 frame1.setResizable(false);
 frame1.setVisible(true);
 frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame1.add(boardPanel);
 }
}

As you can tell, it's meant to represent John Conway's Game of Life on a JFrame. It's my first project using animation and graphics, so I expect there to be a few bad practices. Could anyone provide an honest, critical code review?

Thanks

• mheinzerling: Give better names for button1, frame1, etc.
• abuzittin gillifirca: Since the following suggestions are too obvious to deserve an answer, I'll tell them in this comment: replace boolean[][] emptyBoard = {{.... with boolean[][] emptyBoard = new boolean[10][10] replace new MouseListener with new MouseAdapter and remove empty methods. A just as obvious but not as trivial suggestion is to separate the logic from the swing dependent code.
• abuzittin gillifirca: Some suggestions on how to separate view and model: Move things elsewhere until you do not import anything from java.awt or javax.swing. If you were following single responsibility principle closely the following should be easy tasks: - start two instances of the game in two frames in the same process (from the same main() method) - add a freeze button to enable the grid to evolve but do not update the display and an unfreeze to restart the updates to the display

Answer 1

1. As was suggested in the comments, initialize your matrix as boolean[][] emptyBoard = new boolean[10][10], as in Java booleans will default to false.
2. Document your code: all IDEs will have some support for JavaDoc, use it.
3. Also suggested in the comments, variables should have better names; especially GUI elements (you might not realize the importance of this because in your case you have few elements, but doing this in larger applications will slowly become a royal PITA).
4. Separate logic from presentation. Don't do GUI operations and the game calculations in the same class (i.e. Board).

5. You shouldn't do this:

   for (int[] i: surrounding) {
    try {
    if (board[i[0]][i[1]]) {
    count++;
    }
    }
    catch (ArrayIndexOutOfBoundsException e) {}
   }
   

   Properly defining surrounding should avoid any ArrayIndexOutOfBoundsException.

6. This is mainly a personal preference, but what you have in main() (the GUI parts) I would put in one (or more) separate methods.
7. Another personal preference is using ArratList instead of arrays.