Java Coding Exercise 16

package com.company;

public class Main {

    public static void main(String[] args) {
        System.out.println( sumFirstAndLastDigit(909));
        System.out.println( sumFirstAndLastDigit(2134879));
        System.out.println( sumFirstAndLastDigit(900990));
        System.out.println( sumFirstAndLastDigit(-999999999));
        System.out.println( sumFirstAndLastDigit(-907869));
    }
    public static int sumFirstAndLastDigit(int number) {
        int lastDigit = 0;
        if (number < 0) {
            return -1;

        }
        lastDigit = number % 10;
        int  firstDigit = 0;
        firstDigit = (getReverseNumber(number)) %10;

        return firstDigit + lastDigit;
    }

    public static int getReverseNumber(int number) {
        int middleValue = number;
        int reverse = 0;
        int lastDigit = 0;

        while (middleValue != 0) {
            reverse *= 10;
            lastDigit = middleValue % 10;
            middleValue = middleValue /