add sign function

realDuYuanChao · realDuYuanChao · commit 260f707133db · 2020-10-18T16:01:53.000+08:00
diff --git a/src/main/java/com/examplehub/maths/SignFunction.java b/src/main/java/com/examplehub/maths/SignFunction.java
@@ -0,0 +1,14 @@
+package com.examplehub.maths;
+
+public class SignFunction {
+
+    /**
+     * Sign function algorithm.
+     *
+     * @param number the number to be checked.
+     * @return {@code 1} if number is positive, {@code 0} returned if number is zero, otherwise {@code -1} returned.
+     */
+    public static int signFunction(int number) {
+        return Integer.compare(number, 0);
+    }
+}
diff --git a/src/test/java/com/examplehub/maths/SignFunctionTest.java b/src/test/java/com/examplehub/maths/SignFunctionTest.java
@@ -0,0 +1,16 @@
+package com.examplehub.maths;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class SignFunctionTest {
+    @Test
+    void testSignFunction() {
+        for (int i = 1; i <= 100; i++) {
+            assertEquals(1, SignFunction.signFunction(i));
+            assertEquals(-1, SignFunction.signFunction(-i));
+        }
+        assertEquals(0, SignFunction.signFunction(0));
+    }
+}
