Reduce String - JAVA

// Author : Saurav Kalsoor
// Reduce String - JAVA

import java.util.*;

public class Test {

    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        String n = sc.next();
        System.out.println(reduceString(n));

    }

    public static String reduceString(String originalString){
        if(originalString.length() <= 2) return originalString;

        String newString = "";
        originalString = recurse(originalString, newString);
        return reduceString(originalString);
    }

    public static String recurse(String oldString, String newString){
        if(oldString.isEmpty()) return newString;

        int n = oldString.length();
        if(n == 1){
            return newString + oldString;
        }

        int first = oldString.charAt(0) - '0', last = oldString.charAt(n-1) - '0';
        int sum = first + last;

        oldString = oldString.substring(1, n - 1);
        newString += Integer.toString(sum);
        return recurse(oldString, newString);
    }
}