Adding binary numbers

Question

Does anyone know how to add 2 binary numbers, entered as binary, in Java?

For example, 1010 + 10 = 1100.

Answer 1

To dive into fundamentals:

public static String binaryAddition(String s1, String s2) {
    if (s1 == null || s2 == null) return "";
    int first = s1.length() - 1;
    int second = s2.length() - 1;
    StringBuilder sb = new StringBuilder();
    int carry = 0;
    while (first >= 0 || second >= 0) {
        int sum = carry;
        if (first >= 0) {
            sum += s1.charAt(first) - '0';
            first--;
        }
        if (second >= 0) {
            sum += s2.charAt(second) - '0';
            second--;
        }
        carry = sum >> 1;
        sum = sum & 1;
        sb.append(sum == 0 ? '0' : '1');
    }
    if (carry > 0)
        sb.append('1');

    sb.reverse();
    return String.valueOf(sb);
}