public class BinaryToDecimal {
    public static int binaryToDecimal(String bin, int index) {
        if (index == bin.length()) return 0;
        int bit = bin.charAt(index) - '0';
        return (bit << (bin.length() - index - 1)) + binaryToDecimal(bin, index + 1);
    }

    public static void main(String[] args) {
        String binary = "1011";
        System.out.println("Decimal: " + binaryToDecimal(binary, 0));
    }
}