Depends which order you need to keep the contents of the Collection in. You need to compare the
List Set SortedSet and
Map interfaces to see how they store their contents.
Most List contains methods probably run in linear time, hash methods probably constant time unless the load factor is high, and sorted set methods probably in logarithmic time.
Performance is unpredictable; you will have to try it and see what happens; and good luck with it
[ November 30, 2008: Message edited by: Campbell Ritchie ]