Add Binary

public class Solution {
    public String addBinary(String a, String b) {
      StringBuilder result = new StringBuilder();
      int i = a.length() - 1;
      int j = b.length() - 1;
      int temp = 0;
      char m = '0';
      char n = '0';
      while(i >= 0 || j >= 0){
         if(i < 0 && j >= 0){
            m = '0';
            n = b.charAt(j);
         }
         else if(j < 0 && i >= 0){
            n = '0';
            m = a.charAt(i);
         }
         else{
            m = a.charAt(i);
            n = b.charAt(j);
         }
         result.insert(0, (m + n + temp) % 2);
         temp = (Character.getNumericValue(m) + Character.getNumericValue(n) + temp)/ 2; // change char to int!!!
         i--;
         j--;
      }
      if(temp == 1){
         result.insert(0, 1);
      }
      return result.toString();
    }
    
}