OOPs.java

public class OOPs {
    
}
// OBJECT ORIENTED PROGRAMMING
// Object- Properties and behaviour
// Class 
// #1
// Whatever we do in Java, we do it in a class.
// A class is a user-defined blueprint or prototype from which objects are created.
// - In a class, we have methods and variables.
// - Class will be created in the same java file.
// - We can create any number of classes in a program.
// - Class does not occupy memory.
// Syntax of a class:-
//  class classname
//  {
//   methods, variables
//  }

// #2
// - Every object has two things: properties and methods.
// - When an object of a class is created, the class is said to be instantiated. All the instances share the attributes and the behavior of the class. 
// - Action will be done with the help of methods.
// - We need to specify the access to methods. We will specify it as public if we want it to be called from anywhere else.
// - If we want the method to return any value then we need to specify its return type like int for Integer type values.
// - As Java is a statically typed language so you have to specify the return type in it.

// Syntax of method:-
// = access modifier return type method name()
//  public int add()
//  {
//   statement;
//  }

// #3
// - We need an object to call a method from a different class.
// - Creating an object:-
//  classname reference variable= new classname();
// - reference variable is used to tell that this variable is made to establish a reference between a class.
// - new keyword is used to tell that we have to utilise the space for an object.

// - We can call a method by using the reference variable of the object. 
// - We have to pass the values if we want some operations to be on them.
// - We also have to accept values in a method as well if we pass some values. For this, we have to specify parameters in a method based on the type of passed values.