How to add two binary numbers ?

1. public class AddBinayNumber {
2. 
   
3. public static void main(String[] args) {
4. String s1 = "11";
5. String s2 = "1";
6. String sum = addTwoBinaryNumber(s1, s2);
7. System.out.println(sum);
8. }
9. 
   
10. private static String addTwoBinaryNumber(String s1, String s2) {
11. StringBuilder sb = new StringBuilder();
12. int p1 = s1.length() - 1;
13. int p2 = s2.length() - 1;
14. int carry = 0;
15. while (p1 >= 0 || p2 >= 0) {
16. int sum = carry;
17. if (p1 >= 0) {
18. char ch1 = s1.charAt(p1);
19. sum = sum + ch1 - '0';
20. p1--;
21. }
22. if (p2 >= 0) {
23. char ch2 = s2.charAt(p2);
24. sum = sum + ch2 - '0';
25. p2--;
26. }
27. carry = sum >> 1;
28. sum = sum & 1;
29. sb.append(sum == 0 ? '0' : '1');
30. }
31. if (carry > 0) {
32. sb.append('1');
33. 
    
34. }
35. sb.reverse();
36. return sb.toString();
37. }
38. }

Output: 100