I'm getting Confused over Classes

Question

I bet this is the dumbest question anyone could ever ask but I can't seem to wrap my head around this topic. I understand a Class is used to create an object (when you instantiate it) but what is confusing me is, "When do you know if it is viable to create a Class in a program?".

Say hypothetically your creating a program that gathers an input from the user (be it a name, a number or any other details), use those details to do some calculations and then storing all of it locally. Its basic but would you need to use a class to make the program smoother/faster or more maintainable?

Am I confusing myself?

EDIT: I am mostly using programs like Visual Studio and NetBeans IDE.

Answer 1

1. When do you know if it is viable to create a Class in a program?

I think just about everyone who answers this question will have a slightly different response, but typically, you should use Classes to modularize your program's functionality. In your example, you said that your program might take input from the user, use input to perform some calculations, and persist the user data and calculation results somewhere. You could have the following three classes:

UserInput - handles keyboard input and converting it into some easier-to-process format

Calculator - processes all input after it has been converted

DataPersistence - handles reading/writing from/to disk, or database, or whatever you need.

This way, all of your code isn't just piled up inside a massive Java/C# main() call, you can focus on the smaller parts independently of each other. The interaction between these components is what determines your program's behavior.

2. Its basic but would you need to use a class to make the program smoother/faster or more maintainable?

Classes may actually end up adding overhead to your program because of how objects are referenced in languages like Java or C#, but they make your code much easier to read and modify than if your program was written inside one gigantic function. This is sort of analogous to dividing up math textbooks into chapters. If Algebra, Calculus, and Differential Equations were all condensed into a single chapter of the text book, then the text book wouldn't be very useful to those who want to skip ahead to the Calculus part. The overhead of adding chapter headings is negligible because it allows the author/reader to focus on certain portions of the book.

Likewise, Classes help you divide up your work so it's easier to maintain later. Speed/Performance are generally not affected by how you divide your program into classes, provided you do it intelligently - this is where the real artistry of Object Oriented Design manifests itself :)

Answer 2

For a simple program, like your example, to gather input from the user (name, number, comment), you can easily do this without creating a new class, excluding the fact that languages like C# and Java require a static class to put your main function inside. If you used a non-object oriented language like C, you could easily do it without a class.

For a simple class like you describe, in fact, it might seem like a little extra work to have to create the class (although it is probably negligible). However, that is only because you are referring to a small set of data.

The point where it gets useful to create classes is when you have many pieces of data. The class acts as a way to group that data together, and possibly store it locally as one. You can also add other related methods onto each class that are directly related to the class members.

When you app becomes more complex, say you need to keep track of customers, products, billing information (Credit Card, PayPal, ...), addresses (ship to, and billing), is when classes become extremely valuable in keeping each bit of information together as well as relating each of those larger "bundles" (classes) of information to each other.

You could have a customer who has an order who has a bill to and a shipping address. Each of these classes, itself has many fields inside of it. But you can relate the larger concept of customer to a target shipping address a lot easier with classes.

As far as "When do you know if it is viable to create a Class in a program?", the answer is not always easy, but any time you see data fields which naturally fit together (well, like an address, or a product description or billing information). I wish I had a more concrete answer, but it really depends on what you are building, and what type of data you are working with.

And no, it's not the dumbest question anyone could ever ask! I hope this helps your understanding.

Answer 3

Classes are primarily for us humans to help us organize code. They don't necessarily make software run faster on a computer. When I first learned about classes, I found it helpful to model "real-world" objects. For example, if I wanted to write a program that calculates the area and perimeter of geometrical shapes, I would create a simple Shape class which defines the abstract methods which do the calculations. Then I extend this class to create different kinds of shapes, say Circle, Square, and Triangle. By starting with simple applications of classes and through more programming experience, I have been able to gradually see other places to use classes.

Answer 4

In Java you don't have a choice: you can't write code that's outside of a class.

A class is a template for instances. It encapsulates state and behavior together into a single software component. You write programs by creating instances of classes that interact together to accomplish your goals.

would you need to use a class to make the program smoother/faster or more maintainable?

I can't speak for C#, but in Java you don't have a choice. You either create a single class that does all that in a main class or you break it up into several classes that handle different parts of the problem (e.g. I/O, calculations, persistence, etc.) You have to have one or more classes.

You write classes and create objects from them because they map well to the kind of problems that you want to solve. They're either real objects that model physical things in the world (e.g. Person, Car, Bank, etc.) or reifications of ideas (e.g. PersonFactory, Account, etc.) You choose to write object-oriented code because objects model the problem you'd like to solve well.

Some problems lend themselves to functional programming. There are more than one way to write programs to solve problems.

Answer 5

As you say a class is a construct that allows you to describe a type, which has properties methods and events on it.

In simple situations you can easily get away with not using classes, but in larger, more complex projects having a properly thought out object model makes things so much easier. Easier to maintain, extend, reuse, read.

It may feel like more work at the time (and in most cases it probably is), but it is definitely not wasted effort if you're creating something that will need to be supported.

Answer 6

here is a very simple / easy to understand Tutorial that will help you in learning / understanding C# especially Classes also look at Structs as well

C# Class Tutorial