Java Enums

An enum is a special “class” that represents a group of constants (cannot be changed, like final variables).

Example

enum Speed{
       LOW,
       MEDIUM,
       HIGH
}

The enum constants can be accessed with the dot syntax:

Speed myVar = Speed.HIGH;

Enum is the short form of “enumerations” , which means “specifically listed”.

Example

enum Speed{
       LOW,
       MEDIUM,
       HIGH
}
 
public class EnumClass {
       public static void main (String args[]){
              Speed myVar = Speed.HIGH;
              System.out.println(myVar);
       }
}

Output

HIGH

Enum Inside a Class

We can have an enum inside a class.

Example

public class EnumClass {
       enum Speed{
              LOW,
              MEDIUM,
              HIGH
       }
       public static void main (String args[]){
              Speed myVar = Speed.MEDIUM;
              System.out.println(myVar);
       }
}

Output

MEDIUM

Enum in a Switch Statement

Enums are often used in switch statements to  check for the corresponding case values:

Example

public class EnumClass {
       enum Speed{
              LOW,
              MEDIUM,
              HIGH
       }
       public static void main (String args[]){
              Speed myVar = Speed.MEDIUM;
             
              switch (myVar){
              case LOW:
                     System.out.println("Low speed");
                     break;
              case MEDIUM:
                     System.out.println("Medium speed");
                     break;
              case HIGH:
                     System.out.println("High level");
                     break;
       }
}

Output

Medium speed

Loop through an Enum

The enum type has values() method, which returns an array of all enum constants.. This method is useful when we want to loop through constants of an enum.

Example

In the below example, we use for loop to loop through the constants.

public class EnumClass {
       enum Speed{
              LOW,
              MEDIUM,
              HIGH
       }
       public static void main (String args[]){
             
              for(Speed myVar: Speed.values()) {
                     System.out.println(myVar);
              }
       }
}

Output

LOW
MEDIUM
HIGH

Enums vs. Classes

•  Like Class, an Enum also contains attributes and methods. The only difference is that the enum constants are public, static and final.
• An enum cannot be used to create objects, and it cannot extend other classes (but it can implement interfaces).

Why and When to use Enums?

We use Enums when we use constant values such as month, days, decks of cards, colors etc.