Java Enums
Java Enums
An enum is a special "class" that represents a group of
constants (unchangeable variables, like final variables).
To create an enum, use the enum keyword (instead of class or interface), and separate
the constants with a comma. Note that they should be in uppercase letters:
Example
enum Level {
LOW,
MEDIUM,
HIGH
}
You can access enum constants with the dot syntax:
Level myVar = Level.MEDIUM;
Run example »
Enum is short for "enumerations", which means "specifically listed".
Enum inside a Class
You can also have an enum inside a class:
Example
public class MyClass {
enum Level {
LOW,
MEDIUM,
HIGH
}
public static void main(String[] args) {
Level myVar = Level.MEDIUM;
System.out.println(myVar);
}
}
The output will be:
MEDIUM
Enum in a Switch Statement
Enums are often used in switch statements to check for corresponding values:
Example
enum Level {
LOW,
MEDIUM,
HIGH
}
public class MyClass {
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;
}
}
}
The output will be:
Medium level
Loop Through an Enum
The enum type has a values() method, which returns an array of all enum constants. This method is useful when you want to loop through the constants of an enum:
Example
for (Level myVar : Level.values()) {
System.out.println(myVar);
}
The output will be:
LOW
MEDIUM
HIGH
Difference between Enums and Classes
An enum can, just like a class, have attributes and methods. The only
difference is that enum constants are public, static and final
(unchangeable - cannot be overridden).
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?
Use enums when you have values that you know aren't going to change, like month days, days, colors, deck of cards, etc.
