Task: Elementary cellular automaton
C#: using System;
using System.Collections;
namespace ElementaryCellularAutomaton
{
    class Automata
    {
        BitArray cells, ncells;
        const int MAX_CELLS = 19;

        public void run()
        {
            cells = new BitArray(MAX_CELLS);
            ncells = new BitArray(MAX_CELLS);
            while (true)
            {
                Console.Clear();
                Console.WriteLine("What Rule do you want to visualize");
                doRule(int.Parse(Console.ReadLine()));
                Console.WriteLine("Press any key to continue...");
                Console.ReadKey();
            }
        }

        private byte getCells(int index)
        {
            byte b;
            int i1 = index - 1,
                i2 = index,
                i3 = index + 1;

            if (i1 < 0) i1 = MAX_CELLS - 1;
            if (i3 >= MAX_CELLS) i3 -= MAX_CELLS;

            b = Convert.ToByte(
                4 * Convert.ToByte(cells.Get(i1)) +
                2 * Convert.ToByte(cells.Get(i2)) +
                Convert.ToByte(cells.Get(i3)));
            return b;
        }

        private string getBase2(int i)
        {
            string s = Convert.ToString(i, 2);
            while (s.Length < 8)
            { s = "0" + s; }
            return s;
        }

        private void doRule(int rule)
        {
            Console.Clear();
            string rl = getBase2(rule);
            cells.SetAll(false);
            ncells.SetAll(false);
            cells.Set(MAX_CELLS / 2, true);

            Console.WriteLine("Rule: " + rule + "\n----------\n");

            for (int gen = 0; gen < 51; gen++)
            {
                Console.Write("{0, 4}", gen + ": ");

                foreach (bool b in cells)
                    Console.Write(b ? "#" : ".");

                Console.WriteLine("");

                int i = 0;
                while (true)
                {
                    byte b = getCells(i);
                    ncells[i] = '1' == rl[7 - b] ? true : false;
                    if (++i == MAX_CELLS) break;
                }

                i = 0;
                foreach (bool b in ncells)
                    cells[i++] = b;
            }
            Console.WriteLine("");
        }

    };
    class Program
    {
        static void Main(string[] args)
        {
            Automata t = new Automata();
            t.run();
        }
    }
}

Java: import java.awt.*;
import java.awt.event.ActionEvent;
import javax.swing.*;
import javax.swing.Timer;

public class WolframCA extends JPanel {
    final int[] ruleSet = {30, 45, 50, 57, 62, 70, 73, 75, 86, 89, 90, 99,
        101, 105, 109, 110, 124, 129, 133, 135, 137, 139, 141, 164,170, 232};
    byte[][] cells;
    int rule = 0;

    public WolframCA() {
        Dimension dim = new Dimension(900, 450);
        setPreferredSize(dim);
        setBackground(Color.white);
        setFont(new Font("SansSerif", Font.BOLD, 28));

        cells = new byte[dim.height][dim.width];
        cells[0][dim.width / 2] = 1;

        new Timer(5000, (ActionEvent e) -> {
            rule++;
            if (rule == ruleSet.length)
                rule = 0;
            repaint();
        }).start();
    }

    private byte rules(int lhs, int mid, int rhs) {
        int idx = (lhs << 2 | mid << 1 | rhs);
        return (byte) (ruleSet[rule] >> idx & 1);
    }

    void drawCa(Graphics2D g) {
        g.setColor(Color.black);
        for (int r = 0; r < cells.length - 1; r++) {
            for (int c = 1; c < cells[r].length - 1; c++) {
                byte lhs = cells[r][c - 1];
                byte mid = cells[r][c];
                byte rhs = cells[r][c + 1];
                cells[r + 1][c] = rules(lhs, mid, rhs); 
                if (cells[r][c] == 1) {
                    g.fillRect(c, r, 1, 1);
                }
            }
        }
    }

    void drawLegend(Graphics2D g) {
        String s = String.valueOf(ruleSet[rule]);
        int sw = g.getFontMetrics().stringWidth(s);

        g.setColor(Color.white);
        g.fillRect(16, 5, 55, 30);

        g.setColor(Color.darkGray);
        g.drawString(s, 16 + (55 - sw) / 2, 30);
    }

    @Override
    public void paintComponent(Graphics gg) {
        super.paintComponent(gg);
        Graphics2D g = (Graphics2D) gg;
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);

        drawCa(g);
        drawLegend(g);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame f = new JFrame();
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setTitle("Wolfram CA");
            f.setResizable(false);
            f.add(new WolframCA(), BorderLayout.CENTER);
            f.pack();
            f.setLocationRelativeTo(null);
            f.setVisible(true);
        });
    }
}