comp.lang.java.programmer Google Group

Re: Better way to implement reverse mapping of custom enum ordinals?

nos...@nowhere.com (markspace) — Sat, 12 Dec 2009 17:16:26 UT

This bit here I had to comment on. The whole point of enums is that you
replace int, which is a homogeneous type that appears everywhere in a
program, with a specific class type, which only appears in your API
where it is a valid parameter.
The idea that you then goes back in the other direction and use enums to

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t...@urchin.earth.li (Tom Anderson) — Sat, 12 Dec 2009 16:16:14 UT

Hay guise,
I'm wondering if JCR, aka the Content Repository API for Java, could be
useful to me. I've been reading about it - including reading the spec -
but i'm still not really sure. Does anyone have any hands-on experience
with it?
The thing is, my use is not managing anything really document-like, but

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Re: Better way to implement reverse mapping of custom enum ordinals?

t...@urchin.earth.li (Tom Anderson) — Sat, 12 Dec 2009 13:25:24 UT

You can also trick the constructor-put idea into working by moving the map
into a different class, which can even be an inner class of the enum:
public enum SomeType {
FOO(101),
BAR(100),
GORK(4001);
private static class ByColumnValue {
public static final Map<Integer, SomeType> MAP = new HashMap<Integer, SomeType>();

Re: Better way to implement reverse mapping of custom enum ordinals?

t...@urchin.earth.li (Tom Anderson) — Sat, 12 Dec 2009 13:15:46 UT

You might mean literally what you wrote, but that sounds like a veiled
insult - "your company is doing it wrong". If that is what you meant,
that's childish and presumptuous. There could be a number of very good
reasons why the schema can't change. Perhaps the schema is part of some
bigger app, and David is writing a utility which works alongside it.

Re: JApplet + JNI working only in Safari

qu0llsixf...@gmail.com (Qu0ll) — Sat, 12 Dec 2009 09:16:53 UT

What OS? Are you sure you have the correct native libraries for the OS in
question?

JApplet + JNI working only in Safari

anoop...@gmail.com (nair) — Sat, 12 Dec 2009 08:06:36 UT

Hello techies,
I've developed an applet which is signed and also loads 3rd party
dll's runtime. I'm using JNI to link my DLL's with
JScript.
To my surprise the platform independent JVM fails to load my DLL in
most of the browsers except Safari. In safari the behavior is as
expected. Indeed one of the dll is getting loaded but a second Java

Re: Better way to implement reverse mapping of custom enum ordinals?

newsgroup.spamfil...@virtualinfinity.net (Daniel Pitts) — Sat, 12 Dec 2009 06:34:26 UT

That restriction is going to really suck when requirements dictate a
design change. Glad I don't work at your company.

Re: Better way to implement reverse mapping of custom enum ordinals?

newsgroup.spamfil...@virtualinfinity.net (Daniel Pitts) — Sat, 12 Dec 2009 06:32:30 UT

And a yet better idea is to store the enumeration "name" as a database
"enum" type, if the DB supports it (MySQL does, not sure about others).
The database converts to and from the internal representation (which is
usually integer), but the column value looks like a string.

Re: Better way to implement reverse mapping of custom enum ordinals?

newsgroup.spamfil...@virtualinfinity.net (Daniel Pitts) — Sat, 12 Dec 2009 06:29:25 UT

See inline comments:
public static enum SomeType {
// enum names are usually all caps.
FOO(101), BAR(100), GORK(4001);
// Exposing this as a public final field.
// One of the few times I would actually do that.
public final int columnValue;
SomeType(int columnValue) {
this.columnValue = columnValue;

Re: Better way to implement reverse mapping of custom enum ordinals?

see_webs...@mindprod.com.invalid (Roedy Green) — Sat, 12 Dec 2009 06:19:33 UT

On Fri, 18 Dec 2009 15:42:05 -0800 (PST), "david.karr"
<davidmichaelk...@gmail.com> wrote, quoted or indirectly quoted
someone who said :
If you use Java enums, you can use values()[i] to go from strict
ordinal to enum value.
What you have as your ints are basically short aliases for the enums.
You can build a HashMap in the constructors. See

Re: Better way to implement reverse mapping of custom enum ordinals?

no...@lewscanon.com (Lew) — Sat, 12 Dec 2009 04:58:13 UT

enums generally have few enough values that a linear search is acceptable:
public static MyNumeration fromRepresentation( String rep )
{
for ( MyNumeration numer : values() )
{
if ( numer.toString().equals( rep ) )
{
return numer;
}
}
return valueOf( numer );