BAEL-1212 Guide to Creational Design Patterns (#2932)

* Initial commit for 'Introduction to Creational Design Patterns'

* second commit with some minor fixes and test case additions

* second commit with some minor fixes and test case additions

* BAEL-1212 Guide to Creational Patterns - Made changes as per latest review

* Renamed Toy family to AAnimal family.

core-java/src/test/java/com/baeldung/designpatterns/creational/abstractfactory/AbstractPatternIntegrationTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.designpatterns.creational.abstractfactory;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class AbstractPatternIntegrationTest {
+    @Test
+    public void givenAbstractFactory_whenGettingObjects_thenSuccessful() {
+        AbstractFactory abstractFactory;
+        
+        //creating a brown toy dog
+        abstractFactory = FactoryProvider.getFactory("Toy");
+        Animal toy = abstractFactory.getAnimal("Dog");
+        
+        abstractFactory = FactoryProvider.getFactory("Color");
+        Color color = abstractFactory.getColor("Brown");
+        
+        String result = "A " + toy.getType() + " with " + color.getColor() + " color " + toy.makeSound();
+        assertEquals("A Dog with brown color Barks", result);
+    }
+
+}

core-java/src/test/java/com/baeldung/designpatterns/creational/builder/BuilderPatternIntegrationTest.java

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+package com.baeldung.designpatterns.creational.builder;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class BuilderPatternIntegrationTest {
+    @Test
+    public void whenCreatingObjectThroughBuilder_thenObjectValid() {
+        BankAccount newAccount = new BankAccount
+          .BankAccountBuilder("Jon", "22738022275")
+          .withEmail("jon@example.com")
+          .wantNewsletter(true)
+          .build();
+        
+        assertEquals(newAccount.getName(), "Jon");
+        assertEquals(newAccount.getAccountNumber(), "22738022275");
+        assertEquals(newAccount.getEmail(), "jon@example.com");
+        assertEquals(newAccount.isNewsletter(), true);
+    }
+    
+    @Test
+    public void whenSkippingOptionalParameters_thenObjectValid() {
+        BankAccount newAccount = new BankAccount
+          .BankAccountBuilder("Jon", "22738022275")
+          .build();
+        
+        assertEquals(newAccount.getName(), "Jon");
+        assertEquals(newAccount.getAccountNumber(), "22738022275");
+        assertEquals(newAccount.getEmail(), null);
+        assertEquals(newAccount.isNewsletter(), false);
+    }
+}

core-java/src/test/java/com/baeldung/designpatterns/creational/factory/FactoryIntegrationTest.java

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+package com.baeldung.designpatterns.creational.factory;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class FactoryIntegrationTest {
+
+    @Test
+    public void whenUsingFactoryForSquare_thenCorrectObjectReturned() {
+        Polygon p;
+        PolygonFactory factory = new PolygonFactory();
+        
+        //get the shape which has 4 sides
+        p = factory.getPolygon(4);
+        String result = "The shape with 4 sides is a " + p.getType();
+        
+        assertEquals("The shape with 4 sides is a Square", result);
+    }
+    
+    @Test
+    public void whenUsingFactoryForOctagon_thenCorrectObjectReturned() {
+        Polygon p;
+        PolygonFactory factory = new PolygonFactory();
+        
+        //get the shape which has 4 sides
+        p = factory.getPolygon(8);
+        String result = "The shape with 8 sides is a " + p.getType();
+        
+        assertEquals("The shape with 8 sides is a Octagon", result);
+    }
+}

core-java/src/test/java/com/baeldung/designpatterns/creational/singleton/SingletonIntegrationTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.designpatterns.creational.singleton;
+
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class SingletonIntegrationTest {
+
+    @Test
+    /**
+     * Although there is absolutely no way to determine whether
+     * a class is Singleton, in this test case, we will just 
+     * check for two objects if they point to same instance or 
+     * not. We will also check for their hashcode.
+     */
+    public void whenGettingMultipleObjects_thenAllPointToSame() {
+        //first object
+        Singleton obj1 = Singleton.getInstance();
+        
+        //Second object
+        Singleton obj2 = Singleton.getInstance();
+        
+        assertTrue(obj1 == obj2);
+        assertEquals(obj1.hashCode(), obj2.hashCode());
+    }
+
+}