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Enum Data Type in Java - (BCA / B.Tech)

What is an Enum in Java?

An enum (short for enumeration) is a special data type that represents a fixed set of constants. It is used when a variable can only take one value from a small, predefined set of possible values. Common examples include days of the week, compass directions, or states in a process (e.g., PENDING, PROCESSING, COMPLETED). Enums enhance code readability and prevent errors from using invalid values.

Defining and Using an Enum:

An enum is defined using the enum keyword. The constants are listed in uppercase letters.


// Define an enum for pizza sizes
public enum Size {
    SMALL, MEDIUM, LARGE, EXTRA_LARGE
}

public class PizzaOrder {
    public static void main(String[] args) {
        // Use the enum constant directly
        Size pizzaSize = Size.LARGE;
        
        System.out.println("You ordered a " + pizzaSize + " pizza.");
    }
}

Enums in a `switch` Statement:

Enums are very powerful when used with `switch` statements, as the compiler can check if all enum constants are handled.


Size mySize = Size.MEDIUM;
switch (mySize) {
    case SMALL:
        System.out.println("Small pizza selected.");
        break;
    case MEDIUM:
        System.out.println("Medium pizza selected.");
        break;
    case LARGE:
        System.out.println("Large pizza selected.");
        break;
    default:
        System.out.println("Some other size.");
        break;
}

Key Features of Enums:

Type-Safety: You can't assign an invalid value to an enum variable. For example, Size mySize = "Small"; would cause a compile-time error.
Built-in Methods: Enums come with useful methods. Size.values() returns an array of all constants, allowing you to iterate through them. Size.valueOf("LARGE") converts a string to the corresponding enum constant.
Advanced Capabilities: An enum can have its own methods, constructors, and instance variables, making it much more powerful than simple constants.

Enum Data Type in Java

What is an Enum in Java?

In this Chapter