Basic OOP

OOP stands for Object-Oriented Programming. Writing methods that manipulate data is the essence of procedural programming, whereas object-oriented programming focuses on building objects that hold both data and methods.

Object-Oriented Programming (OOP) is a programming prototype widely used in Java and many other programming languages. In Java, every element is linked to classes and objects, which have their own attributes and methods. The concept of ‘objects’, which are instances of classes, is the focus of it. Each object contains both data (attributes) and methods (functions) that operate on that data. The main principles of OOP in Java are:

• Object
• Class
• Inheritance
• Polymorphism
• Abstraction
• Encapsulation

Class:

In Java, a class functions as a blueprint used to create objects. It acts as a template that specifies the structure and behavior of objects belonging to a specific category. When you instantiate a class by creating an object from it, the resulting object is an instance of that class, inheriting its defined characteristics and behaviors. Let’s describe the concept of class in Java:

1. Class Declaration:

• A class is defined by using the ‘class’ keyword, followed by the chosen class name. This text is generated to be distinct.
• The class name should start with an uppercase letter and follow Java naming conventions (e.g., Account, MyClass, Car, Person

2. Class Members:

• A class can contain various members, such as fields (attributes) and methods (functions).
• Fields represent the data or state of the objects created from the class.
• Methods encapsulate the functionality and operations that objects are capable of executing.

3. Fields (Attributes):

• Fields are variables declared within the class.
• They represent the data associated with each object of the class.
• Fields can be of different data types, such as int, String, boolean, or even other class types.

4. Constructors:

• Constructors are special methods used to initialize objects when they are created from the class.
• The method shares its name with the class and lacks a return type.
• Constructors are typically used to set initial values to the object’s attributes.

5. Methods (Functions):

• Methods are functions defined within the class that operate on the class’s data (fields).
• They define the behavior and actions that the objects can perform.
• Methods can have parameters and return types.

6. Access Modifiers:

• Access modifiers such as public, private, protected, and default (no modifier) are available in Java.
• Access modifiers determine the visibility and accessibility of class members, such as fields and methods, within a program.
• For example, public members are accessible from outside the class, while private members are only accessible within the class itself.

Object:

One of the core ideas of object-oriented programming (OOP) in Java is an object. An object is a live embodiment of a class, actively carrying out the class’s instructions. Once the object is created, it takes up space like other variables in memory, objects in Java are like individual things that you create based on a blueprint (class), and each object can have its own attributes and do specific actions (methods). Each object in Java has a unique identity. Objects are manipulated through references, which are memory addresses pointing to the object

To create an object, you use the new keyword followed by the class constructor. The constructor initializes the object and allocates memory for its attributes

Example:

public class Toyota { //class declaration
    String color;    //Class Properties/Attributes 
    int door;        
    String model;    
    
    Toyota(String color, int door, String model) { //constructor
        this.color = color; //'this' refers to associate Object Name
        this.door = door;
        this.model = model;
    }
    public void print() { //method
        System.out.println( this.color );
        System.out.println( this.door );
        System.out.println( this.model );
    }
}//class
public class ObjectMain {
    public static void main(String[] args) {
       Toyota corolla; // object declare
       corolla = new Toyota("Red", 4,  "Corolla SE"); //instantiate the cleass 
       corolla.print(); //method call by object
       Toyota camry;
       camry = new Toyota("Blue", 2,  "Camry XLE");
       camry.print();
    
   }

}

Output: