Obtaining a powerset of a set in Java

Question

The powerset of {1, 2, 3} is:

{{}, {2}, {3}, {2, 3}, {1, 2}, {1, 3}, {1, 2, 3}, {1}}

Let\'s say I have a Set in Java:<

Answer 1

// input: S
// output: P
// S = [1,2]
// P = [], [1], [2], [1,2]

public static void main(String[] args) {
    String input = args[0];
    String[] S = input.split(",");
    String[] P = getPowerSet(S);
    if (P.length == Math.pow(2, S.length)) {
        for (String s : P) {
            System.out.print("[" + s + "],");
        }
    } else {
        System.out.println("Results are incorrect");
    }
}

private static String[] getPowerSet(String[] s) {
    if (s.length == 1) {
        return new String[] { "", s[0] };
    } else {
        String[] subP1 = getPowerSet(Arrays.copyOfRange(s, 1, s.length));
        String[] subP2 = new String[subP1.length];
        for (int i = 0; i < subP1.length; i++) {
            subP2[i] = s[0] + subP1[i];
        }
        String[] P = new String[subP1.length + subP2.length];
        System.arraycopy(subP1, 0, P, 0, subP1.length);
        System.arraycopy(subP2, 0, P, subP1.length, subP2.length);
        return P;
    }

}