Enum Types (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

Enum Types (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

An enum type is a special data type that enables for a variable to be a set of predefined constants. The variable must be equal to one of the values that have been predefined for it. Common examples include compass directions (values of NORTH, SOUTH, EAST, and WEST) and the days of the week.

Because they are constants, the names of an enum type's fields are in uppercase letters.

In the Java programming language, you define an enum type by using the enum keyword. For example, you would specify a days-of-the-week enum type as:

public enum Day {      SUNDAY, MONDAY, TUESDAY, WEDNESDAY,      THURSDAY, FRIDAY, SATURDAY   }  

You should use enum types any time you need to represent a fixed set of constants. That includes natural enum types such as the planets in our solar system and data sets where you know all possible values at compile time—for example, the choices on a menu, command line flags, and so on.

Read full article from Enum Types (The Java™ Tutorials > Learning the Java Language > Classes and Objects)