Check for string rotation in Java

Given two strings s1 and s2, write a snippet to check whether s2 is a rotation of s1. Strings may contain duplicates.


Input :  s1 = "ABCD", s2 = "CDAB"
Output : True
String s1 is rotation of s2.

Input :  s1 = "ABAD", s2 = "ADAB"
Output : True

Input : s1 = ABCD, and s2 = ACBD 
Output : False

One simple solution is to search first occurrence of s1 in s2. For every match, check if remaining string matches circularly.

An efficient solution is to concatenate s1 with itself. s2 is a rotation of s1 if and only if it is a substring of the rotated string. In java we can either use string contains or indexOf to check for substring.





// Java program to check if two given strings are
//  rotations of each other
class StringRotation {
    /* Function checks if passed strings (str1 and str2)
       are rotations of each other */
    static boolean areRotations(String str1, String str2)
        // There lengths must be same and str2 must be
        // a substring of str1 concatenated with str1.
        return (str1.length() == str2.length()) && 
               ((str1 + str1).contains(str2));
    // Driver method
    public static void main(String[] args)
        String str1 = "AACD";
        String str2 = "ACDA";
        if (areRotations(str1, str2))




Attention reader! Don’t stop learning now. Get hold of all the important Java and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.

My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using or mail your article to See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.