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https://issues.apache.org/jira/browse/LUCENE-1998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12768304#action_12768304
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DM Smith commented on LUCENE-1998:
----------------------------------
bq. changing the order of enum constants is bad, you should always add them at
the end
Is this true?
I did not know how Java serializes enums so I went looking:
See: http://java.sun.com/j2se/1.5.0/docs/guide/serialization/relnotes15.html
Turns out it serializes the text representation of the enum constant and class
info. This is just like the Parameter class.
If I understand it correctly, with this, an enum is resilient to changes in
order. New constants can go in any place (for example, we can later add
LUCENE_291 before LUCENE_30) and not break serialization compatibility.
This is especially good for the future as it allows a path for deprecations.
(E.g. deprecation of o.a.l.d.Field.Index.COMPRESS)
So having LUCENE_CURRENT at the end is fine.
If we wanted it first (or anywhere else) we could have onOrAfter to be:
public boolean onOrAfter(Version other) { return other == LUCENE_CURRENT ||
compareTo(other) >= 0; }
If we wanted to expose version numbering info in the future, I'd suggest the
following pattern (names are unimportant):
LUCENE_29 {
public int getMajor() { return 2; }
public int getMinor() { return 9; }
public int getFix() { return 0; }
}
because it does not require storage and unlike "2900" does not have positional
notation meaning (PIC code), e.g. public int getMajor() { return
int(2900/1000); }
> Use Java 5 enums
> ----------------
>
> Key: LUCENE-1998
> URL: https://issues.apache.org/jira/browse/LUCENE-1998
> Project: Lucene - Java
> Issue Type: Improvement
> Affects Versions: 3.0
> Reporter: DM Smith
> Assignee: Uwe Schindler
> Priority: Minor
> Fix For: 3.0
>
> Attachments: LUCENE-1998_enum.patch, LUCENE-1998_enum.patch,
> LUCENE-1998_enum.patch, LUCENE-1998_enum.patch
>
>
> Replace the use of o.a.l.util.Parameter with Java 5 enums, deprecating
> Parameter.
> Replace other custom enum patterns with Java 5 enums.
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