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  1. Lucene - Core
  2. LUCENE-1369

Eliminate unnecessary uses of Hashtable and Vector



    • Improvement
    • Status: Closed
    • Minor
    • Resolution: Fixed
    • 2.3.2
    • 2.4
    • None
    • None
    • New, Patch Available


      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:

      1. internal but with ArrayList or HashMap would do as well. These can simply be replaced.
      2. internal and synchronization is required. Either leave as is or use a collections synchronization wrapper.
      3. 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.
      4. Generated by JavaCC. (All *.jj files.) Nothing to be done here.
      5. 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.)
      6. As a return value from a package protected method, but synchronization is not used. Change return type.
      7. 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;

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


        1. LUCENE-1369.patch
          87 kB
          DM Smith



            mikemccand Michael McCandless
            dmsmith DM Smith
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