ConstantInterface vs ConstantClass(Enum)

[Seetharaman Venkatasamy]

I know there are many recommendation for Constant class. but some time it is convenient to declare constant in interface. for example say,

I have a specification like below:

interface Election
{
    int ON = 1;
    int OFF = 0;
    int vote();
}

there may be x, y, ..z client who may create extra return like ERROR -1 blah, blah(they may create extra constant class)..... but some may required exactly either ON or OFF. why i should allow this client to create one more file for constant. I could have create one more constant file in my API and serve o client but why the extra file? and client have to read the file also..

what you guys say?

[dennis deems]

I say constants do not belong in an interface. And surely this example is better served by an enum?

[Winston Gutkowski]

Dennis Deems wrote:I say constants do not belong in an interface.

Seconded.

Winston

[Rob Spoor]

Thirded. I really prefer classes like java.sql.Types over interfaces like javax.swing.SwingConstants. Just look at the many classes that implement the latter

[Campbell Ritchie]

It used to be thought it was a good idea to have constants in interfaces, but that caused problems when a class implemented that interface. Those constants became part of the public interface of all those classes. More recent thinking has it that those constants can be put in a class and imported into any classes needing them. You will find a bit more here, including a reference to Joshua Bloch’s book.