Enums (short for enumerations) are a powerful yet underappreciated feature in object-oriented design. They allow you to define a fixed set of named constants that improve clarity, type safety, and maintainability in your system.

Used correctly, enums can make your code more expressive, self-documenting, and resilient to errors.

What is an Enum?

An enum is a special data type that defines a collection of constant values under a single name. Unlike primitive constants or string literals, enums are type-safe, which means you can’t assign just any value to a variable declared as an enum type.

They ensure that a variable can only take one out of a predefined set of valid options.

In short: If a value can only be one of a predefined set of options, use an enum.

Why Use Enums?

Enums provide several key advantages over plain constants or strings:

Avoid “magic values”: No more scattered strings or integers like "PENDING" or 3 in your code.
Improve readability: Enums make your intent clear — OrderStatus.SHIPPED is far more descriptive than 3.
Enable compiler checks: The compiler validates enum usage, catching typos and invalid assignments early.
Support IDE features: Most IDEs provide auto-completion and refactoring tools for enum values.
Reduce bugs: You can’t accidentally assign a random string or number that doesn’t belong to enum.

Example Enums:

Enums are perfect for defining categories or states that rarely change.

Order States (e.g., PENDING, IN_PROGRESS, COMPLETED)
User Roles (e.g., ADMIN, CUSTOMER, DRIVER)
Vehicle Types (e.g., CAR, BIKE, TRUCK)
Directions (e.g., NORTH, SOUTH, EAST, WEST)

By using enums instead of raw strings, you make your system easier to understand and harder to misuse.

Code Examples

Simple Enum

Let’s start with a simple example representing the status of an order in an e-commerce application.

This enum defines a finite set of valid states an order can have. Nothing else is allowed.

Using it in code:

Enums with Properties and Methods

Enums can have additional data and even behavior. This makes them even more powerful.

Let’s consider a Coin enum that represents U.S. coins and their denominations.

Using It in Code:

This is far more elegant and safe than using integers directly.

Enums help you define a fixed set of well-known values, giving structure and clarity to your data. But what if you want to define a common set of behaviors that different classes can implement in their own way?

That’s where Interfaces come in. In the next chapter, we'll dive into interfaces.

Enums

Ashish Pratap Singh