enum (Enumeration) in Java

Last Updated: 28 May, 2022

Enum (also known as Enumeration) was added in Java 5, Enum is a special type of Data-type like Class and Interface. Enum is used to define collections of constants (unchangeable variables) in Java.

The enum keyword is used to declare enums in Java, enum can be declared inside a class or not outside a class but not inside in a method. As per the naming convention, we should already write enums in uppercase (capital letters).

By default all Java enum constants are public, static and final.

Syntax:

enum enum_name { CONSTANT1, CONSTANT2, CONSTANT3 }

How to Define and Use an Enum in Java

Use enum keyword to create an enum in Java, An enum can be defined simply by creating a list of enum constants and separating the constants with a comma (,) sign.

Let's understand enum with the help of given example.

// Creating an enum enum Days { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY; } public class EnumExample { public static void main(String[] args) { Days days = Days.TUESDAY; // Print enum constant System.out.println(days); } }

Output

TUESDAY

Use Enums in if-else Statements

// Creating an enum enum Size { SMALL, MEDIUM, LARGE; } public class EnuminIfelse { public static void main(String[] args) { Size size = Size.MEDIUM; // Using enum in if-else statements if (size == Size.SMALL) { System.out.println("Small Size"); } else if (size == Size.MEDIUM) { System.out.println("Medium Size"); } else if (size == Size.LARGE) { System.out.println("Large Size"); } } }

Output

Medium Size

Use Enums in Switch Statements

// Creating an enum enum Size { SMALL, MEDIUM, LARGE; } public class EnumInSwitchCase { public static void main(String[] args) { Size size = Size.LARGE; switch(size) { case SMALL: System.out.println("Small Size"); break; case MEDIUM: System.out.println("Medium Size"); break; case LARGE: System.out.println("Large Size"); break; default: System.out.println("Default Size"); } } }

Output

Large Size

Important points about 'enum' in Java

• All enums by default extend java.lang.Enum class. An Enum is an Abstract Class in Java.
• An Enum is not instantiated using the new keyword because it has private constructor.
• Enum can not declare as private, protected only public should be declared.
• Every enum constant represents an object of type enum.
• Each enum is implemented internally by using Class.
• Enum can implement one or more interfaces.
• Enum cannot extend another enum and class because it internally extends Enum class.