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

I've used Abdullah Jibaly's approach but using nested classes, which provides a nice way for grouping consts. I've seen this go 3 levels deep and if good names are chosen, it can still work quite well.

One might choose to use final classes for this instead of interface classes to avoid violating Item #19 on Josh Bloch's list (Effective Java 2nd edition).

public final class Const {
    private Const() {} // prevent instantiation

    /** Group1 constants pertain to blah blah blah... */
    public static final class Group1 {
        private Group1() {} // prevent instantiation

        public static final int MY_VAL_1 = 1;
        public static final int MY_VAL_2 = 42;
    }

    /** Group2 constants pertain to blah blah blah... */
    public static final class Group2 {
        private Group2() {} // prevent instantiation

        public static final String MY_ALPHA_VAL = "A";
        public static final String MY_ALPHA_VAL = "B";
    }

}