How do you define a class of constants in Java?

Question

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?

---

Clarifications to some answers:

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.

Answer 1

Use a final class, and define a private constructor to hide the public one.
For simplicity you may then use a static import to reuse your values in another class

public final class MyValues {

  private MyValues() {
    // No need to instantiate the class, we can hide its constructor
  }

  public static final String VALUE1 = "foo";
  public static final String VALUE2 = "bar";
}

in another class :

import static MyValues.*
//...

if (VALUE1.equals(variable)) {
  //...
}