Implementing Factory Pattern With Generics in Java (#12895)

* Implementing the factory pattern with generics.

* Did some modifications. Also added unit test.

* Changed the package name.

patterns-modules/design-patterns-creational/src/test/java/com/baeldung/factorygeneric/FactoryGenericUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.factoryGeneric;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.Date;
+
+// Unit test for the NotifierFactory class.
+public class FactoryGenericUnitTest {
+    
+    // Checks that when the factory is asked to provide a string notifier, the object is an actual string notifier.
+    @Test
+    public void givenStringNotifier_whenEquals_thenTrue() {
+        NotifierFactory factory = new NotifierFactory();
+        Notifier<String> stringNotifier = factory.getNotifier(String.class);
+
+        assertNotNull(stringNotifier, "The object returned by the factory is null!");
+        assertTrue(stringNotifier instanceof Notifier<?>, "The object returned by the factory is not a notifier!");
+    }
+
+    // Checks that when the factory is asked to provide a date notifier, the object is an actual date notifier.
+    @Test
+    public void givenDateNotifier_whenEquals_thenTrue() {
+        NotifierFactory factory = new NotifierFactory();
+        Notifier<Date> dateNotifier = factory.getNotifier(Date.class);
+
+        assertNotNull(dateNotifier, "The object returned by the factory is null!");
+        assertTrue(dateNotifier instanceof Notifier<?>, "The object returned by the factory is not a notifier!");
+    }
+
+    // Checks that when the factory is asked to provide both a date notifier and a string notifier, the objects returned are different.
+    @Test
+    public void givenDateNotifierAndStringNotifier_whenEquals_thenFalse() {
+        NotifierFactory factory = new NotifierFactory();
+        Notifier<String> stringNotifier = factory.getNotifier(String.class);
+        Notifier<Date> dateNotifier = factory.getNotifier(Date.class);
+        
+        assertNotNull(stringNotifier, "The object returned by the factory is null!");
+        assertNotNull(dateNotifier, "The object returned by the factory is null!");
+        assertNotEquals(stringNotifier, dateNotifier, "The string notifier and date notifier objects returned by the factory are actually the same!");
+    }
+
+}