Enums

Imagine you're coding a Vice City mission system and you need to represent the current weather: sunny, rainy, foggy, or stormy. You could use Strings like "sunny" and "rainy", but someone could accidentally type "suny" and your code wouldn't catch the typo until runtime. This is where enums come in

An enum (short for enumeration) is a special type that represents a fixed set of named values. Once you define them, those are the only valid options

enum Weather {
    SUNNY, RAINY, FOGGY, STORMY
}

public class Main {
    public static void main(String[] args) {
        Weather today = Weather.SUNNY;
        System.out.println("Today's weather: " + today);
    }
}

Output

Today's weather: SUNNY

By convention, enum values are written in UPPER_SNAKE_CASE. You access them with the enum name, a dot, then the value: Weather.SUNNY

If you try to use a value that doesn't exist in the enum, the compiler stops everything before the program even runs

enum Weather {
    SUNNY, RAINY, FOGGY, STORMY
}

public class Main {
    public static void main(String[] args) {
        Weather w = Weather.RAINY;   // works
        Weather w2 = Weather.SNOWY;  // ERROR: SNOWY doesn't exist in Weather
    }
}

The compiler catches the mistake before the program even starts. That's one of Java's superpowers

Enums work perfectly with switch statements. Each case handles one possible value

enum Weapon {
    PISTOL, SHOTGUN, AUTOMATIC, ROCKET_LAUNCHER
}

public class Main {
    public static void describeWeapon(Weapon w) {
        switch (w) {
            case PISTOL:
                System.out.println("A trusty sidearm. Low damage, high accuracy.");
                break;
            case SHOTGUN:
                System.out.println("Devastating up close. Tommy's favorite.");
                break;
            case AUTOMATIC:
                System.out.println("High fire rate. Good for intense missions.");
                break;
            case ROCKET_LAUNCHER:
                System.out.println("Overkill? Never heard of it.");
                break;
        }
    }

    public static void main(String[] args) {
        describeWeapon(Weapon.SHOTGUN);
        describeWeapon(Weapon.AUTOMATIC);
    }
}

Output

Devastating up close. Tommy's favorite.
High fire rate. Good for intense missions.

Inside a switch you write just PISTOL, not Weapon.PISTOL. Java already knows you're switching on a Weapon, so it lets you skip the prefix

You can iterate through all values of an enum using the values() method

enum Gang {
    VERCETTI, CUBANS, BIKERS, DIAZ
}

public class Main {
    public static void main(String[] args) {
        for (Gang g : Gang.values()) {
            System.out.println(g);
        }
    }
}

Output

VERCETTI
CUBANS
BIKERS
DIAZ

Gang.values() returns an array of all enum constants in the order they were declared. Useful when you want to process every option

When should you use enums instead of Strings?

• Enums: when you have a fixed, known set of options: days of the week, seasons, difficulty levels, game states
• Strings: when the value is free-form or comes from the user: player names, messages, file paths

If you find yourself writing if (status.equals("active") || status.equals("inactive") || ...), you probably want an enum

Mission: Business Report

Tommy has several businesses in Vice City and wants a quick report. Each business can be in one of a few fixed states: making money, temporarily closed, under renovation, or destroyed by a rival gang. For example, Malibu Club is doing well and making money, Print Works is under renovation, Boatyard is temporarily closed, and Kaufman Cabs was destroyed by a rival gang

Define the possible states as a fixed set of values (Status). Write a method describeStatus that takes a state and prints what it means. In main, store the four business names in a names array (one per state, in the same order as the enum's values). Then iterate over Status.values(); for each state, print the matching business name followed by " - ", then describe the state.

Example

Malibu Club - Active: making money every day
Boatyard - Closed: not generating income right now
Print Works - Renovation: work in progress, opening soon
Kaufman Cabs - Destroyed: needs to be rebuilt from scratch