Object & Classes in Java

In this blog post, we will learn about the basic building blocks of any object-oriented programming language.

1-Classes

2-Objects

3-fields

4-methods

5-constructors

Class:

A class can be defined as a template/blueprint that describes the behaviors/states that the object and its type of support. A class has a certain set of properties.

A class can have

1-Data members

2-Methods

3-Blocks

4-Constructor

5-Class and Interface

Object:

An object is a real-world entity it can be physical as well as logical. An object is also known as an instance of a class. An object has a certain state and behaviors.

An object has three important characteristics:

1-Identity

2-State

3-Behaviors

1-Identity: Each Object identity is typically implemented via a unique ID by JVM. The value of the ID is not visible to the external user. But, it is used internally by the JVM to identify each object.

2-State: Represents data(value) of an object.

3-Behaviors: Represents the functionality(behavior) of an object.

Below is the real-world example of Class and object.

Car, bike, truck these all belong to vehicle class. Objects have also different states and behaviors. For example, the car has states like – color, name, model, speed, Mileage and as well as behaviors - distance travel.

In java class is defined by keyword “class” an object is created by a “new” keyword.

Demo Example:

class vehicle{

String name;

String color;

String model;

int speed;

public void distance ()

{

// Functions are defined here

}

}

 Object Creation in java

The below example shows how to create object in java

class A{

public static void main(String [] args)

{

// creating vechile object

vehicle obj=new vehicle();

// Access the data members of vechile class

obj.name;

obj.distance();  // Access the method of vechile class

}

}