Determines whether the two strings are mutually rotating words

Topic

For a string str, the string that is moved from the front to the back is called the spin word of Str. For example str= "12345", its rotational words have "23451", "34512", "45123", "51234". Given two strings A and B, determine whether A and B are mutually rotating words.

Realize

This is a very flattering implementation, adding the original string one at a time, and using a string-contains method to determine whether to include the matched string as judged

import org.junit.Assert;import org.junit.Test;/** * @author lorem */public class IsRotationTest {    boolean isRotation(String str1, String str2) {        if (str1 == null || str2 == null || str1.length() != str2.length()) {            return false;        }        String str = str1 + str1;        if (str.contains(str2)) {            return true;        }        return false;    }    @Test    public void test() {        String str1 = "abcd";        String str2 = "dcad";        Assert.assertEquals(true,isRotation(str1, str2));    }}

Determines whether the two strings are mutually rotating words