CellularAutomaton

import java.util.Arrays;

public class CellularAutomaton {
  private int[] state;
  private int generation = 0;
  private int[][] pattern = {
      // neighbors(3) and new-state
      { 0, 0, 0, 0 }, { 0, 0, 1, 0 }, { 0, 1, 0, 0 }, { 0, 1, 1, 0 },
      { 1, 0, 0, 1 }, { 1, 0, 1, 1 }, { 1, 1, 0, 1 }, { 1, 1, 1, 1 }
  };

  public CellularAutomaton(int[] state) {
    if (state.length < 1) {
      throw new IllegalArgumentException("state length is short.");
    }
    this.state = new int[state.length + 2]; // 2 for side edge
    int i = 0;
    this.state[i++] = 0; // left edge
    for (; i < state.length + 1; ++i) {
      this.state[i] = state[i - 1];
    }
    this.state[i] = 0; // right edge
  }

  public CellularAutomaton next() {
    int[] new_state = new int[state.length];
    new_state[0] = new_state[state.length - 1] = 0;
    for (int p = 0; p < pattern.length; ++p) {
      for (int i = 0; i < state.length - 2; ++i) {
        if (state[i] == pattern[p][0]
            && state[i + 1] == pattern[p][1]
            && state[i + 2] == pattern[p][2]) {
          new_state[i + 1] = pattern[p][3];
        }
      }
    }
    state = new_state.clone();
    ++generation;
    return this;
  }

  public int getGeneration() {
    return generation;
  }

  public String toString() {
    return
        Integer.toString(getGeneration())
        + Arrays.toString(
            Arrays.copyOfRange(state, 1, state.length - 1));
  }

  public static void main(String[] args) {
    CellularAutomaton ca =
        new CellularAutomaton(new int[] { 0, 1, 0, 0, 0, 1, 0, 1 });
    System.out.println(ca);
    for (int i = 0; i < 10; ++i) {
      System.out.println(ca.next());
    }
  }

}