How to Design A Class?

What is Class and Object in Java OOPS?

Classes and objects are the fundamental components of OOP’s. Often there is a confusion between classes and objects. In this tutorial, we try to tell you the difference between class and object.

First, let’s understand what they are,

What is an Object?

An object is nothing but a self-contained component which consists of methods and properties to make a particular type of data useful. Object determines the behavior of the class. When you send a message to an object, you are asking the object to invoke or execute one of its methods.

From a programming point of view, an object can be a data structure, a variable or a function. It has a memory location allocated. The object is designed as class hierarchies.


What is the Difference Between Object & Class?

class is a blueprint or prototype that defines the variables and the methods (functions) common to all objects of a certain kind.

An object is a specimen of a class. Software objects are often used to model real-world objects you find in everyday life.

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Understand the concept of Java Classes and Objects with an example.

Let’s take an example of developing a pet management system, specially meant for dogs. You will need various information about the dogs like different breeds of the dogs, the age, size, etc.

You need to model real-life beings, i.e., dogs into software entities.

Objects and Classes in Java

Moreover, the million dollar question is, how you design such software? Here is the solution-

First, let’s do an exercise.

You can see the picture of three different breeds of dogs below.

Objects and Classes in Java

Stop here right now! List down the differences between them.

Some of the differences you might have listed out maybe breed, age, size, color, etc. If you think for a minute, these differences are also some common characteristics shared by these dogs. These characteristics (breed, age, size, color) can form a data members for your object.

Objects and Classes in Java

Next, list out the common behaviors of these dogs like sleep, sit, eat, etc. So these will be the actions of our software objects.

Objects and Classes in Java

So far we have defined following things,

Objects and Classes in Java

Now, for different values of data members (breed size, age, and color) in Java class, you will get different dog objects.

Objects and Classes in Java

You can design any program using this OOPs approach.

While creating a class, one must follow the following principles.