EvenCheck

realDuYuanChao · realDuYuanChao · commit 06aaa58b3a9e · 2020-09-27T18:19:52.000+08:00
diff --git a/src/main/java/com/examplehub/maths/EvenCheck.java b/src/main/java/com/examplehub/maths/EvenCheck.java
@@ -0,0 +1,24 @@
+package com.examplehub.maths;
+
+public class EvenCheck {
+
+    /**
+     * Check if a number is even or not using modulus operator.
+     *
+     * @param number the number to be checked.
+     * @return {@code true} if the given number is even, otherwise {@code false}.
+     */
+    public static boolean isEven(int number) {
+        return number % 2 == 0;
+    }
+
+    /**
+     * Check if a number is even or not using & operator.
+     *
+     * @param number the number to be checked.
+     * @return {@code true} if the given number is even, otherwise {@code false}.
+     */
+    public static boolean isEvenFaster(int number) {
+        return (number & 1) == 0;
+    }
+}
diff --git a/src/test/java/com/examplehub/maths/EvenCheckTest.java b/src/test/java/com/examplehub/maths/EvenCheckTest.java
@@ -0,0 +1,42 @@
+package com.examplehub.maths;
+
+import com.examplehub.utils.RandomUtils;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class EvenCheckTest {
+
+    @Test
+    void isEven() {
+        for (int i = -100; i <= 100; i += 2) {
+            assertTrue(EvenCheck.isEven(i));
+        }
+    }
+
+    @Test
+    void isEvenFaster() {
+        for (int i = -100; i <= 100; i += 2) {
+            assertTrue(EvenCheck.isEvenFaster(i));
+        }
+    }
+
+    @Test
+    void testSpeed() {
+        int[] ints = RandomUtils.randomInts(-1000, 1000, 1000);
+
+        long startTime = System.nanoTime();
+        for (int j : ints) {
+            boolean isEven = EvenCheck.isEven(j);
+        }
+        long slowTime = System.nanoTime() - startTime;
+
+        startTime = System.nanoTime();
+        for (int anInt : ints) {
+            boolean isEven = EvenCheck.isEven(anInt);
+        }
+        long fasterTime = System.nanoTime() - startTime;
+
+        assertTrue(fasterTime < slowTime);
+    }
+}
