Below is the syntax highlighted version of Cellular.java
from §5.3 Universality.
/****************************************************************************** * Compilation: javac Cellular.java * Execution: java Cellular N * * Simulates and prints N steps of the Rule 90 cellular automaton. * * Sample output: java Cellular 10 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ******************************************************************************/ public class Cellular { public static void main(String[] args) { int N = Integer.parseInt(args[0]); int CELLS = 2 * N; boolean[] cells = new boolean[CELLS]; // cellular automaton at time t boolean[] old = new boolean[CELLS]; // cellular automaton at time t-1 cells[CELLS/2] = true; for (int t = 1; t < N; t++) { // draw current row for (int i = 0; i < CELLS; i++) { if(cells[i]) StdOut.print("*"); else StdOut.print(" "); } StdOut.println(""); // save current row for (int i = 0; i < CELLS; i++) old[i] = cells[i]; // update cells according to rule 90 for (int i = 1; i < CELLS - 1; i++) cells[i] = old[i-1] ^ old[i+1]; // ^ means XOR } } }