ThueMorse.java

Below is the syntax highlighted version of ThueMorse.java from §1.3 Conditionals and Loops.

/******************************************************************************
 *  Compilation:  javac ThueMorse.java
 *  Execution:    java ThueMorse n
 *
 *  Prints the Thue-Morse sequence, which is defined as follows
 *
 *      Start with 0, and repeatedly flip all the bits and concatenate
 *      it onto the original string.
 *
 *  % java ThueMorse 0
 *  0
 *
 *  % java ThueMorse 1
 *  01
 *
 *  % java ThueMorse 2
 *  0110
 *
 *  % java ThueMorse 3
 *  01101001
 *
 *  % java ThueMorse 4
 *  0110100110010110
 *
 *  % java ThueMorse 5
 *  01101001100101101001011001101001
 *
 ******************************************************************************/

public class ThueMorse {
    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);
        String thue   = "0";
        String morse  = "1";

        for (int i = 1; i <= n; i++) {
            String t = thue;             // save away values
            String m = morse;
            thue  += m;
            morse += t;
        }
        System.out.println(thue);
    }

}