Add String

    public String addDecimal(String num1, String num2) {
        String[] nums1 = num1.split("\\.");
        String[] nums2 = num2.split("\\.");
        String[] res1 = padding(nums1[0], nums2[0], 'L');
        String[] res2 = padding(nums1[1], nums2[1], 'R');
        return addStrings(res1[0] + "." + res2[0], res1[1] + "." + res2[1]);
    }

    public String[] padding(String str1, String str2, char direction) {
        String maxStr = str1.length() > str2.length() ? str1 : str2;
        String minStr = str1.length() > str2.length() ? str2 : str1;
        if (direction == 'L') {
            int i = maxStr.length() - 1, j = minStr.length() - 1;
            while (i >= 0 || j >= 0) {
                if (j < 0) {
                    minStr = "0" + minStr;
                }
                i--;
                j--;
            }
        } else {
            int i = 0, j = 0;
            while (i < maxStr.length() || j < minStr.length()) {
                if (j >= minStr.length()) {
                    minStr = minStr + "0";
                }
                i++;
                j++;
            }
        }
        return new String[] { minStr, maxStr };
    }

    public String addStrings(String num1, String num2) {
        if (num1 == null || num2 == null) {
            return "";
        }
        StringBuilder res = new StringBuilder();
        char[] n1 = num1.toCharArray();
        char[] n2 = num2.toCharArray();
        int i = n1.length - 1;
        int carry = 0;
        while (i >= 0 || carry == 1) {
            if (n1[i] == '.') {
                i--;
                res.append(".");
                continue;
            }
            int d1 = n1[i] - '0';
            int d2 = n2[i] - '0';
            int total = (d1 + d2 + carry);
            int digit = total % 10;
            carry = total / 10;
            res.append(String.valueOf(digit));
            i--;
        }
        return res.reverse().toString();
    }