Java Binary Code

import java.util.Scanner;

/*
 * Java Program to add two binary numbers.
 * You can either write your own method or you 
 * can use Java API for doing binary addition.
 * 
 * input: 1010 + 101
 * output = 1111
 */

public class Main {

  public static void main(String[] args) {

    System.out.println("Welcome to Java program to add two binary numbers");
    Scanner scnr = new Scanner(System.in);

    System.out.println("Please enter first binary number");
    String first = scnr.nextLine();

    System.out.println("Please enter second binary number");
    String second = scnr.nextLine();

    String addition = add(first, second);
    System.out.println("addition of two binary number is : " + addition);

    String sum = sum(first, second);
    System.out.println("Sum of two binary number is : " + sum);

    scnr.close();

  }

  /**
   * Java method to calculate sum of two binary numbers this method calculate
   * sum by first converting binary String to binary numbers and then adding
   * them using binary arithmetic.
   * 
   * @param first
   * @param second
   * @return sum of two given binary numbers
   */
  public static String add(String first, String second) {
    int b1 = Integer.parseInt(first, 2);
    int b2 = Integer.parseInt(second, 2);
    int sum = b1 + b2;
    return Integer.toBinaryString(sum);
  }

  /**
   * Java method to add two binary numbers. This method doesn't use Java API,
   * instead develop it's own logic to perform binary addition.
   * 
   * @param bin1
   * @param bin2
   * @return addition of two binary numbers
   */
  public static String sum(String b1, String b2) {
    int len1 = b1.length();
    int len2 = b2.length();
    int carry = 0;
    String res = "";
    // the final length of the result depends on the bigger length between b1
    // and b,
    // (also the value of carry, if carry = 1, add "1" at the head of result,
    // otherwise)
    int maxLen = Math.max(len1, len2);
    for (int i = 0; i < maxLen; i++) {

      // start from last char of String b1 and b2
      // notice that left side is an int and right side is char
      // so we need to minus the decimal value of '0'
      int p = i < len1 ? b1.charAt(len1 - 1 - i) - '0' : 0;
      int q = i < len2 ? b2.charAt(len2 - 1 - i) - '0' : 0;
      int tmp = p + q + carry;
      carry = tmp / 2;
      res = tmp % 2 + res;
    }
    return (carry == 0) ? res : "1" + res;
  }

}