Javapedia Logo
javapedia
DocumentationProgramsSponsorsPlayground

Java Enums

Learn about Java Enums (Enumerations). Understand how to define constants, use enums in switch statements, and add fields and methods to enums.

An Enum (Enumeration) is a special Java type used to define a collection of constants.

Think of a Menu 📜.

  • Pizza Sizes: SMALL, MEDIUM, LARGE.
  • Days: MONDAY, TUESDAY, ... SUNDAY.
  • Traffic Lights: RED, YELLOW, GREEN.

These values don't change. In Java, we use the enum keyword.

Defining an Enum

enum Level {
  LOW,
  MEDIUM,
  HIGH
}

Accessing Enum Constants

You can access enum constants with the dot syntax:

Level myVar = Level.MEDIUM;
System.out.println(myVar); // Output: MEDIUM

Enums in Switch Statement

Enums are perfect for switch statements because they represent a fixed set of choices.

enum Level {
  LOW,
  MEDIUM,
  HIGH
}

public class Main {
  public static void main(String[] args) {
    Level myVar = Level.MEDIUM;

    switch(myVar) {
      case LOW:
        System.out.println("Low level");
        break;
      case MEDIUM:
        System.out.println("Medium level");
        break;
      case HIGH:
        System.out.println("High level");
        break;
    }
  }
}

Loop Through an Enum

The values() method returns an array of all enum constants.

for (Level l : Level.values()) {
  System.out.println(l);
}

Enums with Fields and Methods

Enums are like classes! They can have attributes and methods.

enum Size {
    SMALL("S"), MEDIUM("M"), LARGE("L");

    private String abbreviation;

    // Constructor (Must be private or package-private)
    Size(String abbreviation) {
        this.abbreviation = abbreviation;
    }

    public String getAbbreviation() {
        return abbreviation;
    }
}

public class Main {
    public static void main(String[] args) {
        Size s = Size.LARGE;
        System.out.println("Size: " + s);
        System.out.println("Abbreviation: " + s.getAbbreviation());
    }
}

Tip 💡: Use Enums whenever you have a fixed set of related constants. It makes your code type-safe and readable. Don't use integers (0, 1, 2) for states; use Enums!

Which method returns all constants of an enum?

Note : Java is a statically-typed language. It means that all variables must be declared before they can be used.

Challenge

Complete this chapter to unlock the next one.

Challenge

Task:

Create an enum 'TrafficLight' with values RED, GREEN, YELLOW. In main, print TrafficLight.RED.

Key Takeaways

  • Fixed Set: Use Enums for a known list of constants (Days, Colors, Status).
  • Type Safety: Prevents invalid values (unlike using int constants).
  • Features: Enums can have fields, methods, and constructors!

Common Pitfalls

[!WARNING] Dynamic Data: Don't use Enums for data that changes often (like User Names). Use them for static categories.

What's Next?

Congratulations! You've covered the core and advanced topics. Back to Home →