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From "DM Smith (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-1369) Eliminate unnecessary uses of Hashtable and Vector
Date Thu, 28 Aug 2008 19:25:44 GMT
Eliminate unnecessary uses of Hashtable and Vector
--------------------------------------------------

                 Key: LUCENE-1369
                 URL: https://issues.apache.org/jira/browse/LUCENE-1369
             Project: Lucene - Java
          Issue Type: Improvement
    Affects Versions: 2.3.2
            Reporter: DM Smith
            Priority: Minor
             Fix For: 2.4


Lucene uses Vector, Hashtable and Enumeration when it doesn't need to. Changing to ArrayList
and HashMap may provide better performance.

There are a few places Vector shows up in the API. IMHO, List should have been used for parameters
and return values.

There are a few distinct usages of these classes:
# internal but with ArrayList or HashMap would do as well. These can simply be replaced.
# internal and synchronization is required. Either leave as is or use a collections synchronization
wrapper.
# As a parameter to a method where List or Map would do as well. For contrib, just replace.
For core, deprecate current and add new method signature.
# Generated by JavaCC. (All *.jj files.) Nothing to be done here.
# As a base class. Not sure what to do here. (Only applies to SegmentInfos extends Vector,
but it is not used in a safe manner in all places. Perhaps, implements List would be better.)
# As a return value from a package protected method, but synchronization is not used. Change
return type.
# As a return value to a final method. Change to List or Map.

In using a Vector the following iteration pattern is frequently used.
for (int i = 0; i < v.size(); i++) {
  Object o = v.elementAt(i);
}

This is an indication that synchronization is unimportant. The list could change during iteration.



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