Check if two string rotation of each other

Check if two string rotation of each other

Suppose we need to check whether string 2 is a rotation of string 1. To find this, we concatenate string 1 with string 1. Then, try to find the string 2 in concatenated string. If string 2 is present in concatenated string then, string 2 is rotation of string 1. String 2 deabc is found on the index 3 in concatenated string. So, deabc is rotation of abcde.

Example:

Input:  Str1=Java, str2=Java
Output: Rotation

Approach

Java

public class StringRotation {
    public static void main(String[] args) {
        String str1 = "Java", str2 = "Java";

        boolean flag = isRotation(str1, str2);
        if (flag) {
            System.out.println("Rotation");
        } else {
            System.out.println("Not a rotation");
        }
    }

    private static boolean isRotation(String str1, String str2) {
        if (str1.length() != str2.length()) {
            return false;
        } else {
            // Concatenate both string
            str1 = str1.concat(str1);

            // Check whether str2 is present in str1
            if (str1.indexOf(str2) != -1)
                return true;
            else
                return false;
        }
    }
}

Approach 

Java

public class StringRotation {
    public static void main(String[] args) {
        String str1 = "Java", str2 = "Java";

        boolean flag = isRotation(str1, str2);
        if (flag) {
            System.out.println("Rotation");
        } else {
            System.out.println("Not a rotation");
        }
    }

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