Fixed class name conflict and Checkstyle errors

Author: Mansi5164

src/main/java/com/thealgorithms/bitmanipulation/PowerOfFour.java

@@ -1,16 +1,26 @@
-package bitmanipulation;
+package com.thealgorithms.bitmanipulation;
 
-public class PowerOfFour {
-    public static boolean isPowerOfFour(int n) {
-        // A power of 4 has only one bit set and that bit is at an even position
-        return n > 0 && (n & (n - 1)) == 0 && (n & 0x55555555) != 0;
+/**
+ * This class provides a method to check if a given number is a power of four.
+ */
+public final class PowerOfFour {
+
+    // Private constructor to prevent instantiation
+    private PowerOfFour() {
+        throw new AssertionError("Cannot instantiate utility class");
     }
 
-    public static void main(String[] args) {
-        int num = 64; // change to test other numbers
-        if (isPowerOfFour(num))
-            System.out.println(num + " is a power of 4.");
-        else
-            System.out.println(num + " is NOT a power of 4.");
+    /**
+     * Checks whether the given integer is a power of four.
+     *
+     * @param n the number to check
+     * @return true if n is a power of four, false otherwise
+     */
+    public static boolean isPowerOfFour(int n) {
+        if (n <= 0) {
+            return false;
+        } else {
+            return (n & (n - 1)) == 0 && (n & 0x55555555) != 0;
+        }
     }
 }

src/test/java/com/thealgorithms/bitmanipulation/PowerOfFour.java

@@ -1,11 +1,21 @@
 package com.thealgorithms.bitmanipulation;
 
-public class PowerOfFour {
+/**
+ * This class provides a method to check if a given number is a power of four.
+ */
+public final class PowerOfFour {
 
+    // Private constructor to prevent instantiation
     private PowerOfFour() {
-        throw new IllegalStateException("Utility class");
+        throw new AssertionError("Cannot instantiate utility class");
     }
 
+    /**
+     * Checks whether the given integer is a power of four.
+     *
+     * @param n the number to check
+     * @return true if n is a power of four, false otherwise
+     */
     public static boolean isPowerOfFour(int n) {
         if (n <= 0) {
             return false;

src/test/java/com/thealgorithms/bitmanipulation/PowerOfFourTest.java

@@ -0,0 +1,33 @@
+package com.thealgorithms.bitmanipulation;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for PowerOfFour class.
+ */
+public final class PowerOfFourTest {
+
+    @Test
+    void testPowerOfFourTrueCases() {
+        Assertions.assertTrue(PowerOfFour.isPowerOfFour(1));
+        Assertions.assertTrue(PowerOfFour.isPowerOfFour(4));
+        Assertions.assertTrue(PowerOfFour.isPowerOfFour(16));
+        Assertions.assertTrue(PowerOfFour.isPowerOfFour(64));
+    }
+
+    @Test
+    void testPowerOfFourFalseCases() {
+        Assertions.assertFalse(PowerOfFour.isPowerOfFour(0));
+        Assertions.assertFalse(PowerOfFour.isPowerOfFour(2));
+        Assertions.assertFalse(PowerOfFour.isPowerOfFour(8));
+        Assertions.assertFalse(PowerOfFour.isPowerOfFour(12));
+    }
+
+    @Test
+    void testNegativeNumbers() {
+        Assertions.assertFalse(PowerOfFour.isPowerOfFour(-4));
+        Assertions.assertFalse(PowerOfFour.isPowerOfFour(-16));
+    }
+}
+