public String concatLastLetters(String a, String b)

Given 2 strings, return the concatentation of the LAST letters of each.

public String concatLastLetters(String a, String b) {
  int lenA = a.length();
  int lenB = b.length();
  String lastA = a.substring(lenA-1);
  String lastB = b.substring(lenB-1);
  String combo = lastA + lastB;
  return combo;
}