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[JAVA-621] core-java-lang-oop-inheritance module

Browse Source 
* Creation

* Moved code from https://www.baeldung.com/java-anonymous-classes

* Moved code from www.baeldung.com/java-polymorphism

* Moved code from www.baeldung.com/java-inheritance

* Moved code from www.baeldung.com/java-variable-method-hiding

* Moved code from https://www.baeldung.com/java-type-casting

* Moved code from https://www.baeldung.com/java-super

* Moved code from www.baeldung.com/java-interfaces

* Moved code from www.baeldung.com/java-abstract-class

* Moved code from www.baeldung.com/java-inner-interfaces

* Moved article references to the new README.md
This commit is contained in:
dupirefr
2020-04-04 11:09:04 +02:00
parent ea61137058
commit 21a98198b6
63 changed files with 44 additions and 25 deletions
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4
core-java-modules/core-java-lang-oop/README.md
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@@ -4,12 +4,8 @@ This module contains articles about Object-oriented programming (OOP) in Java
### Relevant Articles:
- [Guide to hashCode() in Java](https://www.baeldung.com/java-hashcode)
- [Polymorphism in Java](https://www.baeldung.com/java-polymorphism)
- [Method Overloading and Overriding in Java](https://www.baeldung.com/java-method-overload-override)
- [How to Make a Deep Copy of an Object in Java](https://www.baeldung.com/java-deep-copy)
- [Guide to Inheritance in Java](https://www.baeldung.com/java-inheritance)
- [Object Type Casting in Java](https://www.baeldung.com/java-type-casting)
- [Type Erasure in Java Explained](https://www.baeldung.com/java-type-erasure)
- [Variable and Method Hiding in Java](https://www.baeldung.com/java-variable-method-hiding)
- [Object-Oriented-Programming Concepts in Java](https://www.baeldung.com/java-oop)
- [[More -->]](/core-java-modules/core-java-lang-oop-2)

13
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Animal.java
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@@ -1,13 +0,0 @@
package com.baeldung.casting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Animal {
private static final Logger LOGGER = LoggerFactory.getLogger(Animal.class);
public void eat() {
LOGGER.info("animal is eating");
}
}

23
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/AnimalFeeder.java
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@@ -1,23 +0,0 @@
package com.baeldung.casting;
import java.util.List;
public class AnimalFeeder {
public void feed(List<Animal> animals) {
animals.forEach(animal -> {
animal.eat();
if (animal instanceof Cat) {
((Cat) animal).meow();
}
});
}
public void uncheckedFeed(List<Animal> animals) {
animals.forEach(animal -> {
animal.eat();
((Cat) animal).meow();
});
}
}

24
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/AnimalFeederGeneric.java
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@@ -1,24 +0,0 @@
package com.baeldung.casting;
import java.util.ArrayList;
import java.util.List;
public class AnimalFeederGeneric<T> {
private Class<T> type;
public AnimalFeederGeneric(Class<T> type) {
this.type = type;
}
public List<T> feed(List<Animal> animals) {
List<T> list = new ArrayList<T>();
animals.forEach(animal -> {
if (type.isInstance(animal)) {
T objAsType = type.cast(animal);
list.add(objAsType);
}
});
return list;
}
}

16
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Cat.java
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@@ -1,16 +0,0 @@
package com.baeldung.casting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Cat extends Animal implements Mew {
private static final Logger LOGGER = LoggerFactory.getLogger(Cat.class);
public void eat() {
LOGGER.info("cat is eating");
}
public void meow() {
LOGGER.info("meow");
}
}

12
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Dog.java
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@@ -1,12 +0,0 @@
package com.baeldung.casting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Dog extends Animal {
private static final Logger LOGGER = LoggerFactory.getLogger(Dog.class);
public void eat() {
LOGGER.info("dog is eating");
}
}

5
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Mew.java
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@@ -1,5 +0,0 @@
package com.baeldung.casting;
public interface Mew {
public void meow();
}

43
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/ArmoredCar.java
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@@ -1,43 +0,0 @@
package com.baeldung.inheritance;
public class ArmoredCar extends Car implements Floatable, Flyable{
private int bulletProofWindows;
private String model;
public void remoteStartCar() {
// this vehicle can be started by using a remote control
}
public String registerModel() {
return model;
}
public String getAValue() {
return super.model; // returns value of model defined in base class Car
// return this.model; // will return value of model defined in ArmoredCar
// return model; // will return value of model defined in ArmoredCar
}
public static String msg() {
// return super.msg(); // this won't compile.
return "ArmoredCar";
}
@Override
public void floatOnWater() {
System.out.println("I can float!");
}
@Override
public void fly() {
System.out.println("I can fly!");
}
public void aMethod() {
// System.out.println(duration); // Won't compile
System.out.println(Floatable.duration); // outputs 10
System.out.println(Flyable.duration); // outputs 20
}
}

12
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/BMW.java
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@@ -1,12 +0,0 @@
package com.baeldung.inheritance;
public class BMW extends Car {
public BMW() {
super(5, "BMW");
}
@Override
public String toString() {
return model;
}
}

32
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Car.java
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@@ -1,32 +0,0 @@
package com.baeldung.inheritance;
public class Car {
private final int DEFAULT_WHEEL_COUNT = 5;
private final String DEFAULT_MODEL = "Basic";
protected int wheels;
protected String model;
public Car() {
this.wheels = DEFAULT_WHEEL_COUNT;
this.model = DEFAULT_MODEL;
}
public Car(int wheels, String model) {
this.wheels = wheels;
this.model = model;
}
public void start() {
// Check essential parts
// If okay, start.
}
public static int count = 10;
public static String msg() {
return "Car";
}
public String toString() {
return model;
}
}

15
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Employee.java
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@@ -1,15 +0,0 @@
package com.baeldung.inheritance;
public class Employee {
private String name;
private Car car;
public Employee(String name, Car car) {
this.name = name;
this.car = car;
}
public Car getCar() {
return car;
}
}

10
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Floatable.java
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@@ -1,10 +0,0 @@
package com.baeldung.inheritance;
public interface Floatable {
int duration = 10;
void floatOnWater();
default void repair() {
System.out.println("Repairing Floatable object");
}
}

13
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Flyable.java
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@@ -1,13 +0,0 @@
package com.baeldung.inheritance;
public interface Flyable {
int duration = 10;
void fly();
/*
* Commented
*/
//default void repair() {
// System.out.println("Repairing Flyable object");
//}
}

18
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/SpaceCar.java
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@@ -1,18 +0,0 @@
package com.baeldung.inheritance;
public class SpaceCar extends Car implements SpaceTraveller {
@Override
public void floatOnWater() {
System.out.println("SpaceCar floating!");
}
@Override
public void fly() {
System.out.println("SpaceCar flying!");
}
@Override
public void remoteControl() {
System.out.println("SpaceCar being controlled remotely!");
}
}

6
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/SpaceTraveller.java
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@@ -1,6 +0,0 @@
package com.baeldung.inheritance;
public interface SpaceTraveller extends Floatable, Flyable {
int duration = 10;
void remoteControl();
}

38
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/polymorphism/FileManager.java
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@@ -1,38 +0,0 @@
package com.baeldung.polymorphism;
import java.awt.image.BufferedImage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class FileManager {
final static Logger logger = LoggerFactory.getLogger(FileManager.class);
public static void main(String[] args) {
GenericFile file1 = new TextFile("SampleTextFile", "This is a sample text content", "v1.0.0");
logger.info("File Info: \n" + file1.getFileInfo() + "\n");
ImageFile imageFile = new ImageFile("SampleImageFile", 200, 100, new BufferedImage(100, 200, BufferedImage.TYPE_INT_RGB).toString()
.getBytes(), "v1.0.0");
logger.info("File Info: \n" + imageFile.getFileInfo());
}
public static ImageFile createImageFile(String name, int height, int width, byte[] content, String version) {
ImageFile imageFile = new ImageFile(name, height, width, content, version);
logger.info("File 2 Info: \n" + imageFile.getFileInfo());
return imageFile;
}
public static GenericFile createTextFile(String name, String content, String version) {
GenericFile file1 = new TextFile(name, content, version);
logger.info("File 1 Info: \n" + file1.getFileInfo() + "\n");
return file1;
}
public static TextFile createTextFile2(String name, String content, String version) {
TextFile file1 = new TextFile(name, content, version);
logger.info("File 1 Info: \n" + file1.getFileInfo() + "\n");
return file1;
}
}

63
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/polymorphism/GenericFile.java
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@@ -1,63 +0,0 @@
package com.baeldung.polymorphism;
import java.util.Date;
public class GenericFile {
private String name;
private String extension;
private Date dateCreated;
private String version;
private byte[] content;
public GenericFile() {
this.setDateCreated(new Date());
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getExtension() {
return extension;
}
public void setExtension(String extension) {
this.extension = extension;
}
public Date getDateCreated() {
return dateCreated;
}
public void setDateCreated(Date dateCreated) {
this.dateCreated = dateCreated;
}
public String getVersion() {
return version;
}
public void setVersion(String version) {
this.version = version;
}
public byte[] getContent() {
return content;
}
public void setContent(byte[] content) {
this.content = content;
}
public String getFileInfo() {
return "Generic File Impl";
}
public Object read() {
return content;
}
}

41
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/polymorphism/ImageFile.java
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@@ -1,41 +0,0 @@
package com.baeldung.polymorphism;
public class ImageFile extends GenericFile {
private int height;
private int width;
public ImageFile(String name, int height, int width, byte[] content, String version) {
this.setHeight(height);
this.setWidth(width);
this.setContent(content);
this.setName(name);
this.setVersion(version);
this.setExtension(".jpg");
}
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
public int getWidth() {
return width;
}
public void setWidth(int width) {
this.width = width;
}
public String getFileInfo() {
return "Image File Impl";
}
public String read() {
return this.getContent()
.toString();
}
}

44
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/polymorphism/TextFile.java
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@@ -1,44 +0,0 @@
package com.baeldung.polymorphism;
public class TextFile extends GenericFile {
private int wordCount;
public TextFile(String name, String content, String version) {
String[] words = content.split(" ");
this.setWordCount(words.length > 0 ? words.length : 1);
this.setContent(content.getBytes());
this.setName(name);
this.setVersion(version);
this.setExtension(".txt");
}
public int getWordCount() {
return wordCount;
}
public void setWordCount(int wordCount) {
this.wordCount = wordCount;
}
public String getFileInfo() {
return "Text File Impl";
}
public String read() {
return this.getContent()
.toString();
}
public String read(int limit) {
return this.getContent()
.toString()
.substring(0, limit);
}
public String read(int start, int stop) {
return this.getContent()
.toString()
.substring(start, stop);
}
}

9
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/scope/method/BaseMethodClass.java
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@@ -1,9 +0,0 @@
package com.baeldung.scope.method;
public class BaseMethodClass {
public static void printMessage() {
System.out.println("base static method");
}
}

9
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/scope/method/ChildMethodClass.java
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@@ -1,9 +0,0 @@
package com.baeldung.scope.method;
public class ChildMethodClass extends BaseMethodClass {
public static void printMessage() {
System.out.println("child static method");
}
}

8
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/scope/method/MethodHidingDemo.java
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@@ -1,8 +0,0 @@
package com.baeldung.scope.method;
public class MethodHidingDemo {
public static void main(String[] args) {
ChildMethodClass.printMessage();
}
}

13
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/scope/variable/ChildVariable.java
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@@ -1,13 +0,0 @@
package com.baeldung.scope.variable;
/**
* Created by Gebruiker on 5/7/2018.
*/
public class ChildVariable extends ParentVariable {
String instanceVariable = "child variable";
public void printInstanceVariable() {
System.out.println(instanceVariable);
}
}

23
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/scope/variable/HideVariable.java
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@@ -1,23 +0,0 @@
package com.baeldung.scope.variable;
/**
* Created by Gebruiker on 5/6/2018.
*/
public class HideVariable {
private String message = "this is instance variable";
HideVariable() {
String message = "constructor local variable";
System.out.println(message);
}
public void printLocalVariable() {
String message = "method local variable";
System.out.println(message);
}
public void printInstanceVariable() {
System.out.println(this.message);
}
}

13
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/scope/variable/ParentVariable.java
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@@ -1,13 +0,0 @@
package com.baeldung.scope.variable;
/**
* Created by Gebruiker on 5/7/2018.
*/
public class ParentVariable {
String instanceVariable = "parent variable";
public void printInstanceVariable() {
System.out.println(instanceVariable);
}
}

18
core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/scope/variable/VariableHidingDemo.java
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@@ -1,18 +0,0 @@
package com.baeldung.scope.variable;
/**
* Created by Gebruiker on 5/6/2018.
*/
public class VariableHidingDemo {
public static void main(String[] args) {
HideVariable variable = new HideVariable();
variable.printLocalVariable();
variable.printInstanceVariable();
ParentVariable parentVariable = new ParentVariable();
ParentVariable childVariable = new ChildVariable();
parentVariable.printInstanceVariable();
childVariable.printInstanceVariable();
}
}

80
core-java-modules/core-java-lang-oop/src/test/java/com/baeldung/casting/CastingUnitTest.java
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@@ -1,80 +0,0 @@
package com.baeldung.casting;
import org.junit.Test;
import static org.junit.Assert.*;
import java.util.ArrayList;
import java.util.List;
public class CastingUnitTest {
@Test
public void whenPrimitiveConverted_thenValueChanged() {
double myDouble = 1.1;
int myInt = (int) myDouble;
assertNotEquals(myDouble, myInt);
}
@Test
public void whenUpcast_thenInstanceUnchanged() {
Cat cat = new Cat();
Animal animal = cat;
animal = (Animal) cat;
assertTrue(animal instanceof Cat);
}
@Test
public void whenUpcastToObject_thenInstanceUnchanged() {
Object object = new Animal();
assertTrue(object instanceof Animal);
}
@Test
public void whenUpcastToInterface_thenInstanceUnchanged() {
Mew mew = new Cat();
assertTrue(mew instanceof Cat);
}
@Test
public void whenUpcastToAnimal_thenOverridenMethodsCalled() {
List<Animal> animals = new ArrayList<>();
animals.add(new Cat());
animals.add(new Dog());
new AnimalFeeder().feed(animals);
}
@Test
public void whenDowncastToCat_thenMeowIsCalled() {
Animal animal = new Cat();
((Cat) animal).meow();
}
@Test(expected = ClassCastException.class)
public void whenDownCastWithoutCheck_thenExceptionThrown() {
List<Animal> animals = new ArrayList<>();
animals.add(new Cat());
animals.add(new Dog());
new AnimalFeeder().uncheckedFeed(animals);
}
@Test
public void whenDowncastToCatWithCastMethod_thenMeowIsCalled() {
Animal animal = new Cat();
if (Cat.class.isInstance(animal)) {
Cat cat = Cat.class.cast(animal);
cat.meow();
}
}
@Test
public void whenParameterCat_thenOnlyCatsFed() {
List<Animal> animals = new ArrayList<>();
animals.add(new Cat());
animals.add(new Dog());
AnimalFeederGeneric<Cat> catFeeder = new AnimalFeederGeneric<Cat>(Cat.class);
List<Cat> fedAnimals = catFeeder.feed(animals);
assertTrue(fedAnimals.size() == 1);
assertTrue(fedAnimals.get(0) instanceof Cat);
}
}

46
core-java-modules/core-java-lang-oop/src/test/java/com/baeldung/inheritance/AppUnitTest.java
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@@ -1,46 +0,0 @@
package com.baeldung.inheritance;
import com.baeldung.inheritance.*;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;
public class AppUnitTest extends TestCase {
public AppUnitTest(String testName) {
super( testName );
}
public static Test suite() {
return new TestSuite(AppUnitTest.class);
}
@SuppressWarnings("static-access")
public void testStaticMethodUsingBaseClassVariable() {
Car first = new ArmoredCar();
assertEquals("Car", first.msg());
}
@SuppressWarnings("static-access")
public void testStaticMethodUsingDerivedClassVariable() {
ArmoredCar second = new ArmoredCar();
assertEquals("ArmoredCar", second.msg());
}
public void testAssignArmoredCarToCar() {
Employee e1 = new Employee("Shreya", new ArmoredCar());
assertNotNull(e1.getCar());
}
public void testAssignSpaceCarToCar() {
Employee e2 = new Employee("Paul", new SpaceCar());
assertNotNull(e2.getCar());
}
public void testBMWToCar() {
Employee e3 = new Employee("Pavni", new BMW());
assertNotNull(e3.getCar());
}
}

32
core-java-modules/core-java-lang-oop/src/test/java/com/baeldung/polymorphism/PolymorphismUnitTest.java
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@@ -1,32 +0,0 @@
package com.baeldung.polymorphism;
import static org.junit.Assert.*;
import java.awt.image.BufferedImage;
import org.junit.Test;
public class PolymorphismUnitTest {
@Test
public void givenImageFile_whenFileCreated_shouldSucceed() {
ImageFile imageFile = FileManager.createImageFile("SampleImageFile", 200, 100, new BufferedImage(100, 200, BufferedImage.TYPE_INT_RGB).toString()
.getBytes(), "v1.0.0");
assertEquals(200, imageFile.getHeight());
}
// Downcasting then Upcasting
@Test
public void givenTextFile_whenTextFileCreatedAndAssignedToGenericFileAndCastBackToTextFileOnGetWordCount_shouldSucceed() {
GenericFile textFile = FileManager.createTextFile("SampleTextFile", "This is a sample text content", "v1.0.0");
TextFile textFile2 = (TextFile) textFile;
assertEquals(6, textFile2.getWordCount());
}
// Downcasting
@Test(expected = ClassCastException.class)
public void givenGenericFile_whenCastToTextFileAndInvokeGetWordCount_shouldFail() {
GenericFile genericFile = new GenericFile();
TextFile textFile = (TextFile) genericFile;
System.out.println(textFile.getWordCount());
}
}