find sum of first and last digits in java

1
2public class Main {
3
4    public static void main(String[] args) {
5        System.out.println(sumFirstAndLastDigit(1221));
6        System.out.println(sumFirstAndLastDigit(2342));
7        System.out.println(sumFirstAndLastDigit(10));
8        System.out.println(sumFirstAndLastDigit(-123));
9	// write your code here
10    }
11    public static int sumFirstAndLastDigit(int number){
12        if (number<0){
13            return -1;  //checking boundary conditions
14        }
15        else if(number==0){
16            return 0;
17        }
18        else{
19            int lastDigit=number%10; // to extract last significant digit
20            while(number>=10){
21                number=number/10;
22            }
23            int firstDigit=number;
24            return (lastDigit+firstDigit);
25        }
26    }