Where do you keep Constants used throughout your application?

Question

Is interface an acceptable place to store my

public static final Foo bar

Do you extrapolate them to be read from outside of the program? Do you

Answer 1

If you are talking about a simple application the Constants class approach is fine:

public class Constants {
    private Constants() {} // no way to instantiate this class
    public static final String MY_VAL = "123";
}

If you're building a larger app you should be using dependency injection, take a look at How can I inject a property value into a Spring Bean which was configured using annotations?