How do you define a class of constants in Java?

Suppose you need to define a class which all it does is hold constants.

public static final String SOME_CONST = "SOME_VALUE";

What is the preferred way of doing this?

1. Interface
2. Abstract Class
3. Final Class

Which one should I use and why?

Enums - I'm not going to use enums, I am not enumerating anything, just collecting some constants which are not related to each other in any way.

Interface - I'm not going to set any class as one that implements the interface. Just want to use the interface to call constants like so: ISomeInterface.SOME_CONST.