Codewars #6 Calculate String Rotation (6kuy)

#Calculate String Rotation

Write a function that receives two strings and returns n, where n is equal to the number of characters we should shift the first string forward to match the second.

For instance, take the strings "fatigue" and "tiguefa". In this case, the first string has been rotated 5 characters forward to produce the second string, so 5 would be returned.

If the second string isn't a valid rotation of the first string, the method returns -1.

Examples:

"coffee", "eecoff" => 2

"eecoff", "coffee" => 4

"moose", "Moose" => -1

"isn't", "'tisn" => 2

"Esham", "Esham" => 0

"dog", "god" => -1

public class CalculateRotation {
  static int shiftedDiff(String first, String second){
    for(int i=0; i< second.length(); i++){
        if(second.equals(first))
            return i;
        second = second.substring(1)+second.charAt(0);
    }
    return -1;
  }
}

나름 군더더기 없이 했다고 생각했는데 

더 쉬운 방법이 있었다 가장 많은 추천을 받은 코드

public class CalculateRotation {
  static int shiftedDiff(String first, String second){
    if(first.length() !=  second.length())
      return -1;
    return (second+second).indexOf(first);
  }
}