gistfile1.txt

 private static void fb_add() {
        String s1="5.4";
        String s2="0.98";
        
        String[] s1_array = s1.split(".");
        String[] s2_array = s2.split(".");
        
        String pre_s1=s1_array[0];
        String pre_s2=s2_array[0];
        
        String post_s1 = s1_array[1];
        String post_s2 = s2_array[1];
      
        StringBuilder out = new StringBuilder("");
        
        int post_diff = post_s2.length()-post_s1.length();
        int pre_diff = pre_s2.length()-pre_s1.length();
        
        char[] c1 = s1.toCharArray();
        char[] c2 = s2.toCharArray();
        
        int i=s1.length()-1;
        int j=s2.length()-1;
        
        int carry =0;
        
        while(i>=0 || j>=0){
          while(i!=j){
            if(post_diff>0){
                out.append(s2.charAt(j));
                j--;
              }
            else if(post_diff<0){
                out.append(s1.charAt(i));
                i--;
            }
          }
          
          if(c1[i]=='.' && c2[j]=='.'){
            out.append('.'); 
            i--;
            j--;
            continue;
          }
        
          int temp_sum = Character.getNumericValue(c1[i])+Character.getNumericValue(c2[j])+carry;
          int sum = temp_sum %10;
          carry = temp_sum / 10;
          out.append(sum);
          i--;
          j--;
         }
          
        
        if(pre_diff>0){
          int tmp = Character.getNumericValue(s2.charAt(j));
          tmp = tmp +carry;
          out.append(tmp);
          
        } else if(pre_diff<0) {
          int tmp = Character.getNumericValue(s1.charAt(i));
          tmp = tmp +carry;
          out.append(tmp);
        }
        
        if(carry>0){
          out.append(carry);
        }
        
        System.out.print(out.reverse().toString());
    }