BAEL-5915 Added different ways to create an object (#13539)

core-java-modules/core-java-lang-oop-constructors/src/main/java/com/baeldung/objectcreation/objects/ClonableRabbit.java

@@ -0,0 +1,18 @@
+package com.baeldung.objectcreation.objects;
+
+public class ClonableRabbit implements Cloneable {
+
+    String name = "";
+
+    public ClonableRabbit(String name) {
+        this.name = name;
+    }
+    
+    public String getName() {
+        return name;
+    }
+    
+    public Object clone() throws CloneNotSupportedException {
+        return super.clone();
+    }
+}

core-java-modules/core-java-lang-oop-constructors/src/main/java/com/baeldung/objectcreation/objects/Rabbit.java

@@ -0,0 +1,17 @@
+package com.baeldung.objectcreation.objects;
+
+public class Rabbit {
+
+    String name = "";
+    
+    public Rabbit() {
+    }
+    
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

core-java-modules/core-java-lang-oop-constructors/src/main/java/com/baeldung/objectcreation/objects/RabbitType.java

@@ -0,0 +1,7 @@
+package com.baeldung.objectcreation.objects;
+
+public enum RabbitType {
+    PET,
+    TAME,
+    WILD
+}

core-java-modules/core-java-lang-oop-constructors/src/main/java/com/baeldung/objectcreation/objects/SerializableRabbit.java

@@ -0,0 +1,21 @@
+package com.baeldung.objectcreation.objects;
+
+import java.io.Serializable;
+
+public class SerializableRabbit implements Serializable {
+    
+    private static final long serialVersionUID = 2589844379773087465L;
+    
+    String name = "";
+    
+    public SerializableRabbit() {
+    }
+    
+    public String getName() {
+        return name;
+    }
+    
+    public void setName(String name) {
+        this.name = name;
+    }
+}

core-java-modules/core-java-lang-oop-constructors/src/main/java/com/baeldung/objectcreation/utils/CreateRabbits.java

@@ -0,0 +1,71 @@
+package com.baeldung.objectcreation.utils;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.lang.reflect.InvocationTargetException;
+import java.util.function.Supplier;
+
+import com.baeldung.objectcreation.objects.ClonableRabbit;
+import com.baeldung.objectcreation.objects.Rabbit;
+import com.baeldung.objectcreation.objects.RabbitType;
+import com.baeldung.objectcreation.objects.SerializableRabbit;
+
+public final class CreateRabbits {
+
+    public static Rabbit createRabbitUsingNewOperator() {
+        Rabbit rabbit = new Rabbit();
+        
+        return rabbit;
+    }
+
+    public static Rabbit createRabbitUsingClassForName() throws InstantiationException, IllegalAccessException, ClassNotFoundException {
+        Rabbit rabbit = (Rabbit) Class.forName("com.baeldung.objectcreation.objects.Rabbit").newInstance();
+        
+        return rabbit;
+    }
+    
+    public static Rabbit createRabbitUsingClassNewInstance() throws InstantiationException, IllegalAccessException {
+        Rabbit rabbit = Rabbit.class.newInstance();
+        
+        return rabbit;
+    }
+    
+    public static Rabbit createRabbitUsingConstructorNewInstance() throws InstantiationException, IllegalAccessException, IllegalArgumentException,
+            InvocationTargetException, NoSuchMethodException, SecurityException {
+        Rabbit rabbit = Rabbit.class.getConstructor().newInstance();
+        
+        return rabbit;
+    }
+    
+    public static ClonableRabbit createRabbitUsingClone(ClonableRabbit originalRabbit) throws CloneNotSupportedException {
+        ClonableRabbit clonedRabbit = (ClonableRabbit) originalRabbit.clone();
+        
+        return  clonedRabbit;
+    }
+    
+    public static SerializableRabbit createRabbitUsingDeserialization(File file) throws IOException, ClassNotFoundException {
+        try (FileInputStream fis = new FileInputStream(file);
+             ObjectInputStream ois = new ObjectInputStream(fis);) {   
+            return (SerializableRabbit) ois.readObject();
+        }
+    }
+    
+    public static Rabbit createRabbitUsingSupplier() {
+        Supplier<Rabbit> rabbitSupplier = Rabbit::new;
+        Rabbit rabbit = rabbitSupplier.get();
+        
+        return rabbit;
+    }
+    
+    public static Rabbit[] createRabbitArray() {
+        Rabbit[] rabbitArray = new Rabbit[10];
+        
+        return rabbitArray;
+    }
+    
+    public static RabbitType createRabbitTypeEnum() {
+        return RabbitType.PET; //any RabbitType could be returned here, PET is just an example.
+    }
+}

core-java-modules/core-java-lang-oop-constructors/src/test/java/com/baeldung/objectcreation/CreateRabbitsUnitTest.java

@@ -0,0 +1,100 @@
+package com.baeldung.objectcreation;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.ObjectOutputStream;
+import java.lang.reflect.InvocationTargetException;
+
+import org.junit.Test;
+
+import com.baeldung.objectcreation.objects.ClonableRabbit;
+import com.baeldung.objectcreation.objects.Rabbit;
+import com.baeldung.objectcreation.objects.RabbitType;
+import com.baeldung.objectcreation.objects.SerializableRabbit;
+import com.baeldung.objectcreation.utils.CreateRabbits;
+
+public class CreateRabbitsUnitTest {
+
+    @Test
+    public void whenUsingNewOperator_thenRabbitIsReturned() {
+        assertTrue(CreateRabbits.createRabbitUsingNewOperator() instanceof Rabbit);
+    }
+
+    @Test
+    public void whenUsingClassForName_thenRabbitIsReturned() throws InstantiationException, IllegalAccessException, ClassNotFoundException {
+        assertTrue(CreateRabbits.createRabbitUsingClassForName() instanceof Rabbit);
+    }
+    
+    @Test
+    public void whenUsingClassNewInstance_thenRabbitIsReturned() throws InstantiationException, IllegalAccessException {
+        assertTrue(CreateRabbits.createRabbitUsingClassNewInstance() instanceof Rabbit);
+    }
+
+    @Test
+    public void whenUsingConstructorNewInstance_thenRabbitIsReturned() throws InstantiationException, IllegalAccessException, IllegalArgumentException,
+            InvocationTargetException, NoSuchMethodException, SecurityException {
+        assertTrue(CreateRabbits.createRabbitUsingConstructorNewInstance() instanceof Rabbit);
+    }
+    
+    @Test
+    public void givenClonableRabbit_whenUsingCloneMethod_thenClonedRabbitIsReturned() throws CloneNotSupportedException {
+        //given
+        ClonableRabbit originalRabbit = new ClonableRabbit("Peter");
+        
+        //when
+        ClonableRabbit clonedRabbit = CreateRabbits.createRabbitUsingClone(originalRabbit);
+        
+        //then
+        assertTrue(clonedRabbit instanceof ClonableRabbit);
+        assertNotEquals(originalRabbit, clonedRabbit);
+        assertEquals("Peter", clonedRabbit.getName());
+    }
+    
+    @Test
+    public void givenSerializedRabbit_whenDeserializing_thenNewRabbitIsReturned() throws IOException, ClassNotFoundException {        
+        //given
+        SerializableRabbit originalRabbit = new SerializableRabbit();
+        originalRabbit.setName("Peter");
+
+        File resourcesFolder = new File("src/test/resources");
+        resourcesFolder.mkdirs(); //creates the directory in case it doesn't exist
+        
+        File file = new File(resourcesFolder, "rabbit.ser");
+        
+        try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+            ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);) {
+            objectOutputStream.writeObject(originalRabbit);
+        }
+        
+        //when
+        SerializableRabbit newRabbit = CreateRabbits.createRabbitUsingDeserialization(file);
+        
+        //then
+        assertTrue(newRabbit instanceof SerializableRabbit);
+        assertNotEquals(originalRabbit, newRabbit);
+        assertEquals("Peter", newRabbit.getName());
+        
+        //clean up
+        file.delete();
+    }
+    
+    @Test
+    public void whenUsingSupplier_thenRabbitIsReturned() {
+        assertTrue(CreateRabbits.createRabbitUsingSupplier() instanceof Rabbit);
+    }
+    
+    @Test
+    public void whenUsingArrays_thenRabbitArrayIsReturned() {
+        assertTrue(CreateRabbits.createRabbitArray() instanceof Rabbit[]);
+    }
+    
+    @Test
+    public void whenUsingEnums_thenRabbitTypeIsReturned() {
+        assertTrue(CreateRabbits.createRabbitTypeEnum() instanceof RabbitType);
+    }
+}