Comments on: Java Enums can implement Interfaces

By: priya

priya — Wed, 18 Apr 2018 04:22:06 +0000

Enumerations serve the purpose of representing a group of named constants in a programming language. An enum type is a special data type that enables for a variable to be a set of predefined objects or constants.

By: Luis Matos

Luis Matos — Wed, 26 Jun 2013 12:31:25 +0000

Thanks a lot, that’s exactly what I was searching for. Very helpful.
Did you ever check whether there was a better way to work with the static Enum.values()? It would surely improve the solution.

By: David O'Meara

David O'Meara — Fri, 17 Jun 2011 02:40:26 +0000

agreed, but I’m talking about interfaces allowing common behaviour between different enumerated types _because_ they are classes. Hence surprising but should not have been 🙂

By: Bogdan Marian

Bogdan Marian — Thu, 16 Jun 2011 06:45:13 +0000

Hello,
Please note that the Java tutorials clearly states that an enum is in fact a class, so of course it can implement an interface 😉 (http://download.oracle.com/javase/tutorial/java/javaOO/enum.html – “… The enum declaration defines a class …”).

By: David O'Meara

David O'Meara — Thu, 16 Jun 2011 01:00:20 +0000

absolutely, and my initial mistake was in thinking a Java enum was something special or separate within the Java system. As you have said the byte code threats it is Class and it may be that modifying the code to be aware of the Enum superclass (maybe mix in some Generics) could allow me to improve the final code rather than calling the static Enum.values() and then accepting an array of an interface type.
I don’t see this as being widely used, but I found it a handy feature.

By: kjordan

kjordan — Wed, 15 Jun 2011 22:36:05 +0000

Well, an enum does just become in byte code a compiler generated class that extends an actual class called Enum where each value inside the enum is just a static instance inside that generated class which are inserted into an array that values() returns. This means since it already extends Enum you can’t extend anything else, but as you’v realized you can do anything else to it that you can do to a regular class.