Add Power of Four Check (Bit Manipulation)

Author: Shewale41

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

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+/*
+ * TheAlgorithms (https://github.com/TheAlgorithms/Java)
+ * Author: Shewale41
+ * This file is licensed under the MIT License.
+ */
+
+package com.thealgorithms.bitmanipulation;
+
+/**
+ * Check if a given integer is a power of four using bit manipulation.
+ *
+ * <p>A number is a power of four if:
+ * <ul>
+ *   <li>It is positive.</li>
+ *   <li>It has only one set bit in its binary representation.</li>
+ *   <li>The only set bit is in an even position (checked with 0xAAAAAAAA mask).</li>
+ * </ul>
+ *
+ * <p>Example:
+ * 4 -> true (2^2)
+ * 16 -> true (4^2)
+ * 8 -> false (not power of 4)
+ */
+public final class PowerOfFour {
+
+    private PowerOfFour() {
+        // Utility class
+    }
+
+    /**
+     * Checks whether a given integer is a power of four.
+     *
+     * @param n number to check
+     * @return true if n is a power of four, false otherwise
+     */
+    public static boolean isPowerOfFour(int n) {
+        return n > 0 && (n & (n - 1)) == 0 && (n & 0xAAAAAAAA) == 0;
+    }
+}

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

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+/*
+ * TheAlgorithms (https://github.com/TheAlgorithms/Java)
+ * Author: Shewale41
+ * This file is licensed under the MIT License.
+ */
+
+package com.thealgorithms.bitmanipulation;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for {@link PowerOfFour}.
+ */
+public class PowerOfFourTest {
+
+    @Test
+    void testPowerOfFourTrueCases() {
+        assertTrue(PowerOfFour.isPowerOfFour(1));
+        assertTrue(PowerOfFour.isPowerOfFour(4));
+        assertTrue(PowerOfFour.isPowerOfFour(16));
+        assertTrue(PowerOfFour.isPowerOfFour(64));
+        assertTrue(PowerOfFour.isPowerOfFour(256));
+    }
+
+    @Test
+    void testPowerOfFourFalseCases() {
+        assertFalse(PowerOfFour.isPowerOfFour(0));
+        assertFalse(PowerOfFour.isPowerOfFour(2));
+        assertFalse(PowerOfFour.isPowerOfFour(8));
+        assertFalse(PowerOfFour.isPowerOfFour(12));
+        assertFalse(PowerOfFour.isPowerOfFour(-4));
+    }
+}