Object-Oriented Programming (OOP) is a powerful programming paradigm that allows you to organize your code and create reusable software components. Java is an object-oriented programming language, and understanding the core concepts of OOP is crucial to becoming a proficient Java developer. In this screen, we will explore the key concepts of OOP such as classes, objects, inheritance, and polymorphism.

Classes

In OOP, a class is a blueprint or template for creating objects. It defines the attributes (data) and methods (behavior) that an object of that class will have. Think of a class as a blueprint for creating multiple instances of an object with similar characteristics. For example, if we have a Person class, each person object created from that class will have attributes like name, age, and methods like walk(), talk(), etc.

Here's an example of a Person class in Java:

1public class Person {
2
3    // Attributes
4    private String name;
5    private int age;
6
7    // Methods
8    public String getName() {
9        return name;
10    }
11
12    public void setName(String name) {
13        this.name = name;
14    }
15
16    public int getAge() {
17        return age;
18    }
19
20    public void setAge(int age) {
21        this.age = age;
22    }
23
24    public void walk() {
25        System.out.println(name + " is walking.");
26    }
27
28    public void talk() {
29        System.out.println(name + " is talking.");
30    }
31
32}

Objects

An object is an instance of a class. It represents a real-world entity or concept. Objects have state (attributes) and behavior (methods). When you create an object, you are creating a specific instance of a class. For example, if we create an object person from the Person class, we can set the name and age attributes and call the walk() and talk() methods.

Here's an example of creating an object from the Person class:

1Person person = new Person();
2person.setName("John");
3person.setAge(30);
4person.walk();
5person.talk();

Inheritance

Inheritance is a key concept in OOP that allows you to create a new class (child class) by inheriting the properties and methods of an existing class (parent class). The child class can add new attributes and methods or override the existing ones. Inheritance promotes code reuse and helps in creating a hierarchical structure of classes based on a real-world relationship.

Here's an example of inheritance in Java:

1public class Animal {
2
3    private String name;
4
5    public String getName() {
6        return name;
7    }
8
9    public void setName(String name) {
10        this.name = name;
11    }
12
13    public void eat() {
14        System.out.println(name + " is eating.");
15    }
16
17}
18
19public class Dog extends Animal {
20
21    public void bark() {
22        System.out.println(getName() + " is barking.");
23    }
24
25}

Polymorphism

Polymorphism is the ability of an object to take on many forms. In Java, polymorphism is achieved through method overriding and method overloading. Method overriding allows a child class to provide a different implementation of a method that is already defined in its parent class. Method overloading allows multiple methods with the same name but different parameters in a class.

Here's an example of polymorphism in Java using method overriding:

1public class Shape {
2
3    public void draw() {
4        System.out.println("Drawing a shape.");
5    }
6
7}
8
9public class Circle extends Shape {
10
11    public void draw() {
12        System.out.println("Drawing a circle.");
13    }
14
15}

These are the fundamental concepts of Object-Oriented Programming in Java. By understanding and applying these concepts, you will be able to design and develop robust and reusable software solutions.

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}

public class Person {

​

    // Attributes

    private String name;

    private int age;

​

    // Methods

    public String getName() {

        return name;

    }

​

    public void setName(String name) {

        this.name = name;

    }

​

    public int getAge() {

        return age;

    }

​

    public void setAge(int age) {

        this.age = age;

    }

​

    public void walk() {

        System.out.println(name + " is walking.");

    }

​

    public void talk() {

        System.out.println(name + " is talking.");