Object and Class in java (JNNC Technologies)

In this post, we will learn about Object and class in java. As Java is an object-oriented programming language, we need to design our program using Objects and classes.

Object: An entity that has state and behavior may be termed as Object.
For example: Employee has state with name, age and department, and behavior such as working on the assignment.

Class: A class is a blueprint/template that defines state and behavior of objects.
For example: Employee is a class in above example.

Object is an instance of class: As object are created on the basis of blueprint/template that class provides, Object is an instance of the class.

Let’s create a simple class:

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package org.arpit.java2blog;

public class Employee {

 String name;

 String age;

 public void workOnAssignment()

 {

  // Working on assignment

 }

}

Below diagram will explain the structure of class: Class Structure

Let’ s see an example of Object now:

You can create object of above class as below:

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Employee employee1=new Employee();

Objects are stored in heap memory.
When above statement gets called, physical object is created in the memory as below:

Now let’s create two objects i.e. employee1 and employe2 and set name and age for these two objects.

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Employee employee1=new Employee();

employee1.setName("Martin");

employee1.setAge(24); 

Employee employee1=new Employee();

employee1.setName("John");

employee1.setAge(20);