476. Number Complement

import java.math.BigInteger;

class Solution {
  	public  int findComplement(int num) {
		String input = Integer.toBinaryString(num);

		StringBuilder outBuilder = new StringBuilder();
		for (int i = 0; i < input.length(); i++) {
			if (input.charAt(i) == '0')
				outBuilder.append(1);
			else
				outBuilder.append(0);
		}

		BigInteger out = new BigInteger(outBuilder.toString(), 2);
		return out.intValue();
	}
}