Difference between Object and Class in Java

Java is an object-oriented programming language, which means that everything in Java is represented as a class and object. Every entity with state and behavior is an object. And, classes are the templates to create objects. It contains data and functions so that it can later be accessed by their objects wherever and whenever they are needed. The main task of objects is to get the data present in the classes or use the functions in those classes to manipulate the data.

It is compulsory for a class to have an object. Otherwise, it can't be used. But, an object can only be created for an existing class. Read this article to learn more about objects and classes in Java and how they are different from each other.

What are Classes in Java?

A class is a user-defined data type that acts as a blueprint for designing the objects in it. It is said to be a container that stores objects of similar type.

Points to Remember about Java Classes

• Every class consists of data members and member functions which can be accessed by their objects. Here, data members are variables and member functions are methods to manipulate the variables.

• A class is created using the keyword "class". A single class can have more than one object. Once a class is declared, it can have as many as objects it requires.

• Defining a class doesn't allocate any memory for it. Memory is created whenever it is instantiated. A class is declared at the beginning of a program that can be accessed anywhere throughout the program using their objects.

• A class encapsulates the data members and member functions in it. If fruit is considered as a class, then different kinds of fruits such as apple, mango, grapes, etc., are considered as objects.

Features of Java Classes

Following are the benefits of using Classes:

• Classes promote the concept of data encapsulation whose main goal is data hiding. It prevents unwanted modification and accessing of data by others. A class cannot be accessed unless it is called by its object

• Large code can be broken into classes that helps to reuse the code.

• It allows inheritance. One class can inherit the functions of other classes. Class that inherit properties is known as a sub class or derived class and the other one from which properties are inherited is known as a super class or base class

What are Objects in Java?

An instance of class is known as an object. It is a real- world entity that is used to access the data members and member functions of a class. An object is said to be a variable for class.

Every time an object is created, memory is allocated for it. The methods of a class can be accessed every time when an object is invoked.

Each and every object has an associated state and behavior. If we consider cat as a class, it consists of information of different breeds of cats, which are its different objects. Each object has some common attributes such as breed, color, age, etc. These elements form the data members of that class and the functions those objects perform are eating, sleeping, walking, etc., which are known as their member functions. So, as these data members are unique to each object, we get different objects for the class "cat".

Based on their work, objects are classified into the following types:

• Function objects

• Container objects

• Immutable objects

• Factory objects

Features of Java Objects

Here are some of the benefits of using Objects:

• Objects are used to access the class members

• We can invoke and use the classes anywhere in the code

• They are used to change the data

• Objects allow easy debugging

Example of Objects and Classes in Java

In the following example, Puppy is a class and myPuppy is an object:

public class Puppy {
   public Puppy(String name) {
      // This constructor has one parameter, name.
      System.out.println("Passed Name is: " + name);
   }
   public static void main(String []args) {
      // Following statement would create an object myPuppy
      Puppy myPuppy = new Puppy("tommy");
   }
}

Output

If we compile and run the above program, then it will produce the following output:

Passed Name is: tommy

Differences: Objects vs Classes

The following table highlights the major differences between Objects and Classes:

Conclusion

Classes and objects together protect data and helps in achieving data abstraction, encapsulation, polymorphism, inheritance etc., hence, these classes and objects form the base of object-oriented programming.