Problem with the game of life

Question

I am working on the implementation of Conway Java games in life as a personal project for myself. So far this works, but the rules go wrong. The expected patterns do not appear, as they should. Is there something wrong with my code?

import javax.swing.*; import java.awt.*; import java.awt.event.*; public class Cell extends JComponent implements MouseListener { private int row, col; private boolean isLiving; public Cell(int r, int c) { this.row = r; this.col = c; this.addMouseListener(this); } public void isAlive(int neighbors) { if (this.isLiving) { if (neighbors < 2) { this.isLiving = false; } else if (neighbors == 2 || neighbors == 3) { this.isLiving = true; } else if (neighbors > 3) { this.isLiving = false; } } else { if (neighbors == 3) { this.isLiving = true; } } } public boolean isLiving() { return this.isLiving; } public void paintComponent(Graphics g) { if (this.isLiving) { g.fillRect(0, 0, 10, 10); } else { g.drawRect(0, 0, 10, 10); } } public void mouseClicked(MouseEvent e) { this.isLiving = !this.isLiving; } public void mouseEntered(MouseEvent e) { } public void mouseExited(MouseEvent e) { } public void mousePressed(MouseEvent e) { } public void mouseReleased(MouseEvent e) { } } 

Answer 1

I suspect that ¹ problem with your code is that it sets the cells to be alive or dead as soon as neighbors are checked. This caused my earlier versions of this code to fail. This change in state should be delayed until the entire grid (biosphere) has been verified.

This example shows typical Game of Life behavior.

• Please note that “suspicions are not answers”, so it’s better to place SSCCE.

 import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.Random; public class GameOfLife extends JPanel { private int row, col; private boolean isLiving; public static Random random = new Random(); public GameOfLife(int r, int c) { this.row = r; this.col = c; MouseListener listener = new MouseAdapter() { public void mouseClicked(MouseEvent e) { isLiving = !isLiving; repaint(); } }; this.addMouseListener(listener); isLiving = random.nextBoolean(); } public boolean isAlive(int neighbors) { boolean alive = false; if (this.isLiving) { if (neighbors < 2) { alive = false; } else if (neighbors == 2 || neighbors == 3) { alive = true; } else if (neighbors > 3) { alive = false; } } else { if (neighbors == 3) { alive = true; } } return alive; } public void setAlive(boolean alive) { isLiving = alive; } public boolean isLiving() { return this.isLiving; } public void paintComponent(Graphics g) { super.paintComponent(g); if (this.isLiving) { g.fillRect(0, 0, getWidth() - 1, getHeight() - 1); } else { g.drawRect(0, 0, getWidth() - 1, getHeight() - 1); } } public static void main(String[] args) { final int s = 40; final GameOfLife[][] biosphere = new GameOfLife[s][s]; final JPanel gui = new JPanel(new GridLayout(s, s, 2, 2)); for (int ii = 0; ii < s; ii++) { for (int jj = 0; jj < s; jj++) { GameOfLife cell = new GameOfLife(ii, jj); cell.setPreferredSize(new Dimension(10, 10)); gui.add(cell); biosphere[ii][jj] = cell; } } ActionListener al = new ActionListener() { public void actionPerformed(ActionEvent ae) { boolean[][] living = new boolean[s][s]; for (int ii = 0; ii < s; ii++) { for (int jj = 0; jj < s; jj++) { int top = (jj > 0 ? jj - 1 : s - 1); int btm = (jj < s - 1 ? jj + 1 : 0); int lft = (ii > 0 ? ii - 1 : s - 1); int rgt = (ii < s - 1 ? ii + 1 : 0); int neighbors = 0; if (biosphere[ii][top].isLiving()) { neighbors++; } if (biosphere[ii][btm].isLiving()) { neighbors++; } if (biosphere[lft][top].isLiving()) { neighbors++; } if (biosphere[lft][btm].isLiving()) { neighbors++; } if (biosphere[lft][jj].isLiving()) { neighbors++; } if (biosphere[rgt][jj].isLiving()) { neighbors++; } if (biosphere[rgt][top].isLiving()) { neighbors++; } if (biosphere[rgt][btm].isLiving()) { neighbors++; } living[ii][jj] = biosphere[ii][jj].isAlive(neighbors); } } for (int ii = 0; ii < s; ii++) { for (int jj = 0; jj < s; jj++) { biosphere[ii][jj].setAlive(living[ii][jj]); } } gui.repaint(); } }; Timer timer = new Timer(50, al); timer.start(); JOptionPane.showMessageDialog(null, gui); timer.stop(); } }