Find If A String is Rotation of Another String

answer_rotation

/* algorithm checkRotation(string s1, string s2) 
  if( len(s1) != len(s2))
    return false
  if( substring(s2,concat(s1,s1))
    return true
  return false
end */

//In Java:

boolean isRotation(String s1,String s2) {
    return (s1.length() == s2.length()) && ((s1+s1).indexOf(s2) != -1);
}

string_rotation

Hello. When i was searching a portal find a good interview question. There is answer of that question.
 
Question:
 
There are two String string1 and string2. how can you check if string1 is a rotated version of string2.
 
Example: 
 
If string1 = "github" then the following are some of its rotated versions:
 
"ithubg"
"hubgit"
 
but "githbu" is not a rotated version