+1
On Mar 21, 2008, at 1:32 PM, Bill Shannon wrote:
> Ken Paulsen wrote:
>> Lloyd, Bill and others:
>> To make sure I understand correctly, let me see if I can repeat
>> back what you're saying...
>> If you define a constant (public static final), for example:
>> public static final String C = "hello";
>> ...then another class references that code, it will be contained in
>> bytecode (i.e. it won't look at the orginal C). In other words, if
>> you change "hello" to "goodbye" w/o recompiling all classes using
>> C, you'll still have "hello" in those classes that weren't
>> recompiled.
>
> Correct.
>
>> However... if you define your "constant" like this:
>> private static String getC() { return "hello" }
>> public static final String C = getC();
>> Or even:
>> public static final String C;
>> static { C = "hello"; }
>> Then code refering to "C" *WILL* refer back to the class instead of
>> keeping it local via bytecode. This is arguably not a constant now
>> (although public static final, it cannot be "inlined" by
>> other .class code). In other words, if you change "hello" to
>> "goodbye" and ONLY compile the class which defines C, it will still
>> be seen in ALL classes referencing C (i.e. no more "hello" anywhere).
>
> Correct.
>
>> Is that right? And if so, what is your recommendation or design
>> pattern that we should follow? It was not clear (to me) from the
>> email exchange. Which if these should be preferred:
>> * Enum
>> * "public static final" initialized via a static method
>> * "public static final" initialized via a static block (probably
>> the same thing to the JVM??)
>> * No "public static final" use static getter method instead
>> * or ??
>
> Don't use Strings for enumerated values that aren't externally defined
> (e.g., in a protocol spec). Use enums.
>
> If the constant is externally defined (e.g., MIME types, charset
> names, etc.), feel free to use, e.g,
>
> public static final String PLAIN_TEXT = "text/plain";
>
> If the constant represents a default, and you want the ability to
> change the default in the future, provide the value via a public
> getDefaultFoo() method.
>
> While the static block initializer works, I'm not sure that's ever
> the right answer.
>
> Maybe we should look at a few examples of where you run into this
> issue?
> Some real examples might help us create and understand the general
> rules.
>
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Lloyd L Chambers
lloyd.chambers_at_sun.com
Sun Microsystems, Inc