Game Of Life, some questions

[Henrik Persson]

Hello!

I'm new to Java, and this is my first "real" project that I'm actually satisfied with, so I thought I'd share it with you. Took a few days to write.
It's a version of the famous Game Of Life by John Conway, where the cells are represented by checkboxes (only because making some other graphic version would be too advanced for me).
It looks alright, you can choose three different sizes and four different speeds. The layout might not be correct for all systems (it's optimized for OSX), but just a simple resize of the window so the checkboxes form a square pattern will do the trick.

Some questions:

-The checkCell()-method seems extremely clunky and awkward, and I guess there must be a better way to do it, any tips? Algorithms?
-The reason I put an infinite loop in the startGame()-method is because I kept getting exceptions when trying to stop and start the game, something about how threads work. Is there a better way to do this (without making a complete rewrite of the entire program)?
-Is there any way to make the gui platform independent?

Have fun! Code below:

GameOfLifeCell-class:

public class GameOfLifeCell {
	
	private boolean isAlive;
	private byte adjacentAlive;
	
	public boolean getStatus() {
		return isAlive;
	}
	
	public void setStatus(boolean b) {
		isAlive = b;
	}
	
	public int getAdjacent() {
		return adjacentAlive;
	}
	
	public void addAdjacent() {
		adjacentAlive++;
	}
	
	public void reset() {
		adjacentAlive = 0;
	}
	
	public void changeStatus() {
		if (isAlive) {
			isAlive = false;
		} else {
			isAlive = true;
		}
	}
}

GameOfLife-class:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

class GameOfLife {

	private int gridSize;
	private int generations;
	private JComboBox gridBox;
	private GameOfLifeCell[] cells;
	private JCheckBox[] checkBoxCells;
	private boolean[] result;
	private int cellsIndex = 0;
	private boolean running;
	private JButton startButton;
	private JButton stopButton;
	private JButton clearButton;
	private String[] speeds = {"Slow", "Normal", "Ultra", "Extra"};
	private JComboBox speedBox;
	private JLabel generationsLabel;
	Runnable loopStarter = new LoopStarter();
	Thread looper = new Thread(loopStarter);

	public static void main(String[] args) {
		GameOfLife game = new GameOfLife();
		game.setUp();
	}
	
	void setUp() {
		JFrame frame = new JFrame("Game Of Life");
		JPanel mainPanel = new JPanel();
		JPanel bottomPanel = new JPanel();
		JLabel gridLabel = new JLabel("Choose size:");
		String[] gridSizes = {"8 x 8", "16 x 16", "24 x 24"};
		gridBox = new JComboBox(gridSizes);
		JButton okButton = new JButton("OK!");
		
		mainPanel.add(gridLabel);
		mainPanel.add(gridBox);
		bottomPanel.add(okButton);
		okButton.addActionListener(new GoListener());
		
		frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
		frame.getContentPane().add(BorderLayout.SOUTH, bottomPanel);
		frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
		frame.setSize(200, 100);
		frame.setVisible(true);
	}
	
	void go() {
		JFrame frame = new JFrame("Game Of Life");
		JPanel mainPanel = new JPanel();
		JPanel bottomPanel = new JPanel();
		startButton = new JButton("Start");
		stopButton = new JButton("Stop");
		clearButton = new JButton("Clear");
		JLabel speedLabel = new JLabel("Speed:");
		generationsLabel = new JLabel("Generations: " + generations);
		speedBox = new JComboBox(speeds);
		
		cells = new GameOfLifeCell[gridSize];
		checkBoxCells = new JCheckBox[gridSize];
		result = new boolean[gridSize];
		
		for (int i = 0; i < gridSize; i++) {
			cells[i] = new GameOfLifeCell();
			checkBoxCells[i] = new JCheckBox();
			mainPanel.add(checkBoxCells[i]);
			checkBoxCells[i].addActionListener(new CheckBoxListener(i));
		}
		
		mainPanel.add(startButton);
		mainPanel.add(stopButton);
		mainPanel.add(clearButton);
		bottomPanel.add(speedLabel);
		bottomPanel.add(speedBox);
		bottomPanel.add(generationsLabel);
		
		startButton.addActionListener(new StartListener());
		stopButton.addActionListener(new StopListener());
		clearButton.addActionListener(new ClearListener());
		startButton.setEnabled(true);
		stopButton.setEnabled(false);
		
		frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
		frame.getContentPane().add(BorderLayout.SOUTH, bottomPanel);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		if (gridSize == 256) {
			frame.setSize(550, 540);
		} else if (gridSize == 64) {
			frame.setSize(290, 320);
		} else {
			frame.setSize(800, 770);
		}
		
		frame.setVisible(true);
		looper.start();
	}
	
	void startGame() {
		int speed;
		
		while (true) {										//keeps the thread running to avoid
															//exceptions when starting/stopping
			while (!running) {
				try {
					Thread.sleep(100);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		
			while (running) {
				String speedSelection = (String) speedBox.getSelectedItem();
		
				if (speedSelection == "Slow") {
					speed = 500;
				} else if (speedSelection == "Ultra") {
					speed = 80;
				} else if (speedSelection == "Extra") {
					speed = 30;
				} else {
					speed = 150;
				}
			
				for (int i = 0; i < (Math.sqrt(gridSize)); i++) {
					for (int j = 0; j < (Math.sqrt(gridSize)); j++) {
						checkCell(j, i);
						result[cellsIndex] = cells[cellsIndex].getStatus();
						cellsIndex++;
					}
				}
			
				cellsIndex = 0;
				
				for (int i = 0; i < gridSize; i++) {
					if (!cells[i].getStatus() && cells[i].getAdjacent() == 3) {
						cells[i].setStatus(true);
					} else if (cells[i].getStatus() && (cells[i].getAdjacent() == 2 || cells[i].getAdjacent() == 3)) {
						cells[i].setStatus(true);
					} else {
						cells[i].setStatus(false);
					}
				}
			
				for (int i = 0; i < gridSize; i++) {
					cells[i].reset();
				}
		
				updateCheckBoxes(result);
				generations++;
				generationsLabel.setText("Generations: " + generations);
				
				try {
					Thread.sleep(speed);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}
	}
	
	void checkCell(int xCoord, int yCoord) {
		int ns = (int) Math.sqrt(gridSize);					// north & south cells
		int nwse = (int) (Math.sqrt(gridSize) + 1);			// northwest & southeast cells
		int nesw = (int) (Math.sqrt(gridSize) - 1);			// northeast & southwest cells
		
		if (xCoord == 0 && yCoord == 0) {					// top left cell
			if (cells[(cellsIndex + 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
		
		if (xCoord == (Math.sqrt(gridSize) - 1) && yCoord == 0) {	// top right cell
			if (cells[(cellsIndex - 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
		
		if (xCoord == 0 && yCoord == (Math.sqrt(gridSize) - 1)) {	// bottom left cell
			if (cells[(cellsIndex + 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
		
		if (xCoord == (Math.sqrt(gridSize) - 1) && 
		yCoord == (Math.sqrt(gridSize) - 1)) { 						// bottom right cell
			if (cells[(cellsIndex - 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
		
		if ((xCoord > 0 && xCoord < (Math.sqrt(gridSize) - 1)) && 
		(yCoord == 0)) {											// top row
			if (cells[(cellsIndex - 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
		
		if ((xCoord == 0) && (yCoord > 0 && 
		yCoord < (Math.sqrt(gridSize) - 1))) {						// left row
			if (cells[(cellsIndex + 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
		
		if ((xCoord == (Math.sqrt(gridSize) - 1)) && 
		(yCoord > 0 && yCoord < (Math.sqrt(gridSize) - 1))) {		// right row
			if (cells[(cellsIndex - 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
	
		if ((xCoord > 0 && xCoord < (Math.sqrt(gridSize) - 1)) && 
		(yCoord == (Math.sqrt(gridSize) - 1))) {					// bottom row
			if (cells[(cellsIndex - 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
		
		if ((xCoord > 0 && xCoord < (Math.sqrt(gridSize) - 1)) && 
		(yCoord > 0 && yCoord < (Math.sqrt(gridSize) - 1))) {		// the rest
			if (cells[(cellsIndex - 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + 1)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nesw)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + ns)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex - nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
			
			if (cells[(cellsIndex + nwse)].getStatus()) {
				cells[cellsIndex].addAdjacent();
			}
		}
	}
	
	void updateCheckBoxes(boolean[] list) {
		for (int i = 0; i < gridSize; i++) {
			checkBoxCells[i].setSelected(list[i]);
		}
	}
	
	class LoopStarter implements Runnable {
		public void run() {
			startGame();
		}
	}
	
	class GoListener implements ActionListener {
		public void actionPerformed(ActionEvent ev) {
			String gridSizeSelected = (String) gridBox.getSelectedItem();
			if (gridSizeSelected == "8 x 8") {
				gridSize = 64;
			} else if (gridSizeSelected == "16 x 16") {
				gridSize = 256;
			} else {
				gridSize = 576;
			}
			go();
		}
	}
		
	class StartListener implements ActionListener {
		public void actionPerformed(ActionEvent ev) {
			running = true;
			startButton.setEnabled(false);
			stopButton.setEnabled(true);
		}
	}
	
	class StopListener implements ActionListener {
		public void actionPerformed(ActionEvent ev) {
			running = false;
			startButton.setEnabled(true);
			stopButton.setEnabled(false);
		}
	}
	
	class ClearListener implements ActionListener {
		public void actionPerformed(ActionEvent ev) {
			for (int i = 0; i < gridSize; i++) {
				cells[i].setStatus(false);
				result[i] = false;
			}
			updateCheckBoxes(result);
			generations = 0;
			generationsLabel.setText("Generations: " + generations);
		}
	}
	
	class CheckBoxListener implements ActionListener {
		int cellNumber;
		
		public CheckBoxListener(int num) {
			cellNumber = num;
		}
			
		public void actionPerformed(ActionEvent ev) {
			cells[cellNumber].changeStatus();
		}
	}
}

[Paul Clapham]

I think you made things a lot harder for yourself by implementing the array of cells as a one-dimensional array.

[Unnar Björnsson]

I made this with javascript once, small project that was fun to do. You can take a look at it here it allows you to initialize the board and then press start, stop or reset. Just select view source in the browser to see the code. Since it is javascript that is similar to java syntax wise and since these kind of problem solving are language independent you might get some ideas from it.
Note: This is probably not the best or fastest way to implement this, it was just some pet project of mine I did for fun there is probably something that could be written better, also the code is not commented.

[Henrik Persson]

Paul Clapham wrote:I think you made things a lot harder for yourself by implementing the array of cells as a one-dimensional array.

I wrote this program while reading the Head First Java book, and it wasn't until I finished the program that I found out about multi-dimensional arrays in the appendix, and it crossed my mind that I could have used one of those instead, but I fail to see how that would improve my code. Can you be more specific? Keep in mind that I am a total newbie to programming!

Unnar Björnsson wrote:I made this with javascript once, small project that was fun to do. You can take a look at it here it allows you to initialize the board and then press start, stop or reset. Just select view source in the browser to see the code. Since it is javascript that is similar to java syntax wise and since these kind of problem solving are language independent you might get some ideas from it.
Note: This is probably not the best or fastest way to implement this, it was just some pet project of mine I did for fun there is probably something that could be written better, also the code is not commented.

Thanks a lot! Google Chrome freezes when I try to view your code however, I'll try it in a different browser.