Java
Enum fields
Learn to add fields to enum constants.
Add fields to an enum
An enum constant can carry extra information. To do this you add a field and a constructor inside the enum. Each constant passes a value to the constructor.
enum Coffee {
SMALL("küçük"), LARGE("büyük");
String label;
Coffee(String label) {
this.label = label;
}
}
The constructor is always private; no new constants can be created from outside. The value is written in parentheses next to the constant and the constructor receives it. This way each constant comes with its own data and the code reads better.
Accessing fields
You access an enum constant's field with a dot. The constructor fills the field; you only read it. The field is usually made final, since constants do not change.
Coffee c = Coffee.LARGE;
System.out.println(c.label); // büyük
Multiple fields can be added too, for example a label and a price. The constructor parameter order must be respected. Making fields public final allows outside access; making them private and returning them via a method is also common.
Exercise Print the coffee label
Define a Coffee enum with SMALL and LARGE constants. Each constant takes a String label (SMALL gets küçük, LARGE gets büyük). Print the label of the LARGE constant.
Show example solution
enum Coffee {
SMALL("küçük"), LARGE("büyük");
String label;
Coffee(String label) { this.label = label; }
}
// inside main:
System.out.println(Coffee.LARGE.label);
Test yourself
-
Pass a value to the constructor
enum Coffee {
SMALL("küçük"), LARGE("____");
String label;
Coffee(String label) { this.label = label; }
}
Show answer
enum Coffee {
SMALL("küçük"), LARGE("büyük");
String label;
Coffee(String label) { this.label = label; }
}
-
What access level is an enum constructor?
- public
- private
- default (package)
- protected
Show answer
private — an enum constructor is always private; no new constants can be created from outside.
-
Match each concept to its description
- label
- Constant's label
- Coffee(String)
- Constructor
- this.label
- Assignment
- SMALL("küçük")
- Value passed
Next lesson: Enum methods
