Fwd: Cleanup patch: Change from Vector/Hashtable to ArrayList/HashMap

Some old 1.0 'Collections' (namely Vector and HashTable) where marked
obsolete, they won't disappear beacause they are too widely used, but they
are very inefficient, so they have better alternatives (ArrayList and
HashMap), event if you want an synchronized List or Map you should use
Collections.synchronized[Collection|Map|List|Set] and not use the old
classes.

However same uses of Vector don't work with newer classes, for example, the
method set won't work on ArrayList (ArrayList with size 10 and set at
position 20, you get Exception, on Vector it works).

So, excluding the example above, it is a good thing to replace Vector by
List/ArrayList and Hashtable by Map/HashMap.
In some case LinkedList is better than ArrayList.

Luis Flores

On Sun, May 6, 2012 at 8:59 PM, Robin Rosenberg
<robin(dot)rosenberg(at)dewire(dot)com>wrote:

> dmp skrev 2012-05-06 20.03:
>
> Mikko Tiihonen wrote:
>> > Hi,
>> >
>> > Here are two small cleanup patches.
>> >
>> > First one replaces all Vector references with List (usage) and
>> ArrayList
>> > (creation).
>> > Second replaces all Hashtable references with Map (usage) and HashMap
>> > (creation).
>> >
>> > Reasons:
>> > * Theoretically faster since the ArrayList/HashMap are not synchronized
>> > * Using interfaces makes changing of List/Map implementations easier at
>> > later time
>> > * Vector/Hashtable were deprecated already in Java 1.2
>>
>> My JDK 6 documentation gives no indication that either Vector or Hashtable
>> as being deprecated. Rather them being retrofitted into the Collectionss
>> Framework at 1.2. The main difference being that as you said they are
>> synchronized, which a developer may wish to have for that type of data
>> structure.
>>
>
> They are not deprecated in the "this might go away" sense, but it was
> discovered
> that having self-synchronized collection classes rarely is enough to
> provide
> thread safety, rather synchronization usually has to be handled in a larger
> scope than the individual method call. Therefore, if you think Vector makes
> your code thread-safe, you need to think again. Even if works it usually a
> very expensive way of accomplishing the goal.
>
> -- robin
>
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