Merge branch 'master' of https://github.com/JonCook/tutorials

core-java-modules/core-java-lang-oop/.gitignore

@@ -0,0 +1,26 @@
+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+*.txt
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-modules/core-java-lang-oop/README.md

@@ -0,0 +1,16 @@
+## Core Java Lang OOP
+
+This module contains articles about Object-oriented programming (OOP) in Java
+
+### Relevant Articles: 
+- [Guide to hashCode() in Java](https://www.baeldung.com/java-hashcode)
+- [A Guide to the Static Keyword in Java](https://www.baeldung.com/java-static)
+- [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)
+- [The “final” Keyword in Java](https://www.baeldung.com/java-final)
+- [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)
+- [[More -->]](/core-java-modules/core-java-lang-oop-2)

core-java-modules/core-java-lang-oop/pom.xml

@@ -0,0 +1,59 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-lang-oop</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-lang-oop</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <!-- web -->
+        <!-- marshalling -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>${jackson.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>${gson.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-lang-oop</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <gson.version>2.8.2</gson.version>
+        <!-- testing -->
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+
+</project>

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Animal.java

@@ -0,0 +1,13 @@
+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");
+    }
+
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/AnimalFeeder.java

@@ -0,0 +1,23 @@
+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();
+        });
+    }
+
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/AnimalFeederGeneric.java

@@ -0,0 +1,24 @@
+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;
+    }
+
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Cat.java

@@ -0,0 +1,16 @@
+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");
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Dog.java

@@ -0,0 +1,12 @@
+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");
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/casting/Mew.java

@@ -0,0 +1,5 @@
+package com.baeldung.casting;
+
+public interface Mew {
+    public void meow();
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/deepcopy/Address.java

@@ -0,0 +1,59 @@
+package com.baeldung.deepcopy;
+
+import java.io.Serializable;
+
+public class Address implements Serializable, Cloneable {
+
+    @Override
+    public Object clone() {
+        try {
+            return (Address) super.clone();
+        } catch (CloneNotSupportedException e) {
+            return new Address(this.street, this.getCity(), this.getCountry());
+        }
+    }
+
+    private static final long serialVersionUID = 1740913841244949416L;
+    private String street;
+    private String city;
+
+    private String country;
+
+    public Address(Address that) {
+        this(that.getStreet(), that.getCity(), that.getCountry());
+    }
+
+    public Address(String street, String city, String country) {
+        this.street = street;
+        this.city = city;
+        this.country = country;
+    }
+
+    public Address() {
+    }
+
+    public String getStreet() {
+        return street;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public String getCountry() {
+        return country;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public void setCountry(String country) {
+        this.country = country;
+    }
+}
+

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/deepcopy/User.java

@@ -0,0 +1,48 @@
+package com.baeldung.deepcopy;
+
+import java.io.Serializable;
+
+public class User implements Serializable, Cloneable {
+
+    private static final long serialVersionUID = -3427002229954777557L;
+    private String firstName;
+    private String lastName;
+    private Address address;
+
+    public User(String firstName, String lastName, Address address) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+        this.address = address;
+    }
+
+    public User(User that) {
+        this(that.getFirstName(), that.getLastName(), new Address(that.getAddress()));
+    }
+
+    public User() {
+    }
+
+    @Override
+    public Object clone() {
+        User user;
+        try {
+            user = (User) super.clone();
+        } catch (CloneNotSupportedException e) {
+            user = new User(this.getFirstName(), this.getLastName(), this.getAddress());
+        }
+        user.address = (Address) this.address.clone();
+        return user;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public Address getAddress() {
+        return address;
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/finalkeyword/BlackCat.java

@@ -0,0 +1,5 @@
+package com.baeldung.finalkeyword;
+
+public class BlackCat {
+
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/finalkeyword/BlackDog.java

@@ -0,0 +1,6 @@
+package com.baeldung.finalkeyword;
+
+public class BlackDog extends Dog {
+    // public void sound() {
+    // }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/finalkeyword/Cat.java

@@ -0,0 +1,18 @@
+package com.baeldung.finalkeyword;
+
+public final class Cat {
+
+    private int weight;
+
+    public int getWeight() {
+        return weight;
+    }
+
+    public void setWeight(int weight) {
+        this.weight = weight;
+    }
+
+    public void methodWithFinalArguments(final int x) {
+        // x=1;
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/finalkeyword/Dog.java

@@ -0,0 +1,7 @@
+package com.baeldung.finalkeyword;
+
+public class Dog {
+    
+    public final void sound() {
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/hashcode/entities/User.java

@@ -0,0 +1,42 @@
+package com.baeldung.hashcode.entities;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class User {
+
+    private final Logger logger = LoggerFactory.getLogger(User.class);
+    private long id;
+    private String name;
+    private String email;
+
+    public User(long id, String name, String email) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null)
+            return false;
+        if (this.getClass() != o.getClass())
+            return false;
+        User user = (User) o;
+        return id == user.id && (name.equals(user.name) && email.equals(user.email));
+    }
+
+    @Override
+    public int hashCode() {
+        int hash = 7;
+        hash = 31 * hash + (int) id;
+        hash = 31 * hash + (name == null ? 0 : name.hashCode());
+        hash = 31 * hash + (email == null ? 0 : email.hashCode());
+        logger.info("hashCode() method called - Computed hash: " + hash);
+        return hash;
+    }
+    // getters and setters here
+    
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/ArmoredCar.java

@@ -0,0 +1,43 @@
+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
+    }
+    
+    
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/BMW.java

@@ -0,0 +1,12 @@
+package com.baeldung.inheritance;
+
+public class BMW extends Car {
+    public BMW() {
+    	super(5, "BMW");
+    }
+	
+	@Override
+    public String toString() {
+    	return model;
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Car.java

@@ -0,0 +1,32 @@
+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;
+    } 
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Employee.java

@@ -0,0 +1,15 @@
+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;
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Floatable.java

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

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/Flyable.java

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

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/SpaceCar.java

@@ -0,0 +1,18 @@
+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!");
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/inheritance/SpaceTraveller.java

@@ -0,0 +1,6 @@
+package com.baeldung.inheritance;
+
+public interface SpaceTraveller extends Floatable, Flyable {
+    int duration = 10;
+    void remoteControl();
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/initializationguide/User.java

@@ -0,0 +1,53 @@
+package com.baeldung.initializationguide;
+
+import java.io.Serializable;
+
+public class User implements Serializable, Cloneable {
+    private static final long serialVersionUID = 1L;
+    static String forum;
+    private String name;
+    private int id;
+
+    {
+        id = 0;
+        System.out.println("Instance Initializer");
+    }
+
+    static {
+    	forum = "Java";
+        System.out.println("Static Initializer");
+    }
+
+    public User(String name, int id) {
+        super();
+        this.name = name;
+        this.id = id;
+    }
+
+    public User() {
+        System.out.println("Constructor");
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    @Override
+    protected Object clone() throws CloneNotSupportedException {
+        return this;
+    }
+
+}
+

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/methodoverloadingoverriding/application/Application.java

@@ -0,0 +1,26 @@
+package com.baeldung.methodoverloadingoverriding.application;
+
+import com.baeldung.methodoverloadingoverriding.model.Car;
+import com.baeldung.methodoverloadingoverriding.model.Vehicle;
+import com.baeldung.methodoverloadingoverriding.util.Multiplier;
+
+public class Application {
+    
+    public static void main(String[] args) {
+        Multiplier multiplier = new Multiplier();
+        System.out.println(multiplier.multiply(10, 10));
+        System.out.println(multiplier.multiply(10, 10, 10));
+        System.out.println(multiplier.multiply(10, 10.5));
+        System.out.println(multiplier.multiply(10.5, 10.5));
+        
+        Vehicle vehicle = new Vehicle();
+        System.out.println(vehicle.accelerate(100));
+        System.out.println(vehicle.run());
+        System.out.println(vehicle.stop());
+        
+        Vehicle car = new Car();
+        System.out.println(car.accelerate(80));
+        System.out.println(car.run());
+        System.out.println(car.stop());
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/methodoverloadingoverriding/model/Car.java

@@ -0,0 +1,9 @@
+package com.baeldung.methodoverloadingoverriding.model;
+
+public class Car extends Vehicle {
+
+    @Override
+    public String accelerate(long mph) {
+        return "The car accelerates at : " + mph + " MPH.";
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/methodoverloadingoverriding/model/Vehicle.java

@@ -0,0 +1,16 @@
+package com.baeldung.methodoverloadingoverriding.model;
+
+public class Vehicle {
+    
+    public String accelerate(long mph) {
+        return "The vehicle accelerates at : " + mph + " MPH.";
+    }
+    
+    public String stop() {
+        return "The vehicle has stopped.";
+    }
+    
+    public String run() {
+        return "The vehicle is running.";
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/methodoverloadingoverriding/util/Multiplier.java

@@ -0,0 +1,16 @@
+package com.baeldung.methodoverloadingoverriding.util;
+
+public class Multiplier {
+    
+    public int multiply(int a, int b) {
+        return a * b;
+    }
+    
+    public int multiply(int a, int b, int c) {
+        return a * b * c;
+    }
+    
+    public double multiply(double a, double b) {
+        return a * b;
+    }
+}

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/polymorphism/FileManager.java

@@ -0,0 +1,38 @@
+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;
+    }
+
+}