feat(strings): add StringRotation to check if one string is a rotatio…

src/main/java/com/thealgorithms/strings/StringRotation.java

@@ -0,0 +1,28 @@
+package com.thealgorithms.strings;
+
+public final class StringRotation {
+
+    private StringRotation() {
+        throw new UnsupportedOperationException("Utility class");
+    }
+
+    /**
+     * Checks if str2 is a rotation of str1.
+     *
+     * @param str1 the original string
+     * @param str2 the string to check for rotation
+     * @return true if str2 is a rotation of str1, false otherwise
+     */
+    public static boolean isRotation(String str1, String str2) {
+        if (str1 == null || str2 == null) {
+            return false;
+        }
+
+        if (str1.length() != str2.length()) {
+            return false;
+        }
+
+        String concatenated = str1 + str1;
+        return concatenated.contains(str2);
+    }
+}

src/test/java/com/thealgorithms/strings/StringRotationTest.java

@@ -0,0 +1,30 @@
+package com.thealgorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+public class StringRotationTest {
+
+    @Test
+    void testValidRotation() {
+        assertTrue(StringRotation.isRotation("waterbottle", "erbottlewat"));
+    }
+
+    @Test
+    void testInvalidRotation() {
+        assertFalse(StringRotation.isRotation("hello", "world"));
+    }
+
+    @Test
+    void testDifferentLengths() {
+        assertFalse(StringRotation.isRotation("abc", "abcd"));
+    }
+
+    @Test
+    void testNullInput() {
+        assertFalse(StringRotation.isRotation(null, "abc"));
+        assertFalse(StringRotation.isRotation("abc", null));
+    }
+}