Programming Challenges

public class TMNTDemo {
    String[] tmnt = { "donatello", "leonardo", "michaelangelo", "raphael" };
    int nTmnt = tmnt.length;
    
    /*
     * Prints all 2^n subsets of the Teenage Mutant Ninja Turtles
     */
    public static void main(String[] args) {
        new TMNTDemo().run();
    }
    
    public void run() {
        for (int mask = 0; mask < (1 << nTmnt); mask++) {
            System.out.printf("Subset %2d [%04d]:", mask, Integer.parseInt(Integer.toString(mask, 2)));
            System.out.println(getSet(mask));
        }
    }
    
    public String getSet(int mask) {
        StringBuilder sb = new StringBuilder();
        
        for (int i = 0; i < nTmnt; i++) {
            if ((mask & (1 << i)) != 0) {
                sb.append(String.format(" %15s", tmnt[i]));
            } else {
                sb.append(String.format(" %15s", ""));
            }
        }
        
        return sb.toString();
    }

}

private boolean nextPerm(int[] a) {
    if (a.length <= 1) return false;
    int i = a.length - 1;
    while (a[i - 1] >= a[i]) {
        if (--i == 0) return false;
    }
    int j = a.length;
    while (a[j - 1] <= a[i - 1]) {
        if (--j == 0) return false;
    }
    swap(a, i - 1, j - 1);
    i++;
    j = a.length;
    while (i < j) {
        swap(a, i - 1, j - 1);
        i++; j--;
    }
    return true;
}