Enums, short for enumerations in Java are a group of named constants that you can define in an array-like structure. They are useful for when you want to create a bunch of related values.

Defining an Enum

Let's dive straight into it and define an enum using the enum keyword:

JAVA
enum Fruit { APPLE, ORANGE, BANANA }

This enum we have created is named Fruit and it contains three items in it. Keep in mind that it is convention to capitalize all the names.

Inside a class, it can look like this:

JAVA
public class Main { enum Fruit { APPLE, ORANGE, BANANA } public static void main(String[] args) { } }

Using an Enum value

Now that we have our enum, we can decide to use it. A common way enums are used are inside a switch statement.

Let's see how that looks:

JAVA
public class Main { enum Fruit { APPLE, ORANGE, BANANA } public static void main(String[] args) { Fruit fruit = Fruit.APPLE; switch(fruit) { case APPLE: System.out.println("An apple was found!"); break; case ORANGE: System.out.println("An orange was found!"); break; case BANANA: System.out.println("A banana was found!"); break; } } }
BASH
An apple was found!

Looping through Enums

Instead of using an enum one at a time, you can loop through them all by using the values() method which returns an array of all the enum values. This then allows you to loop over all of them:

JAVA
public class Main { enum Fruit { APPLE, ORANGE, BANANA } public static void main(String[] args) { for (Fruit fruit : Fruit.values()) { System.out.println(fruit); } } }
BASH
APPLE ORANGE BANANA

For the most part, enums are used when you know the value of them will not change and there's a finite number of them, since they are constant. Real world examples of good cases to use enums include the months in a year, a list of US states, time zones, and the planets in our solar system, to name a few.

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