The introduction of the Collections API by Sun in JDK 1.2 has been a
boon to quick and effective Java programming. Ready access to
powerful data structures has accelerated development by reducing
the need for custom container classes around each core object.
Most Java2 APIs are significantly easier to use because of the
Collections API. However, there are certain holes left unfilled
by Sun's implementations, and the Jakarta-Commons Collections
Component strives to fulfill them. Among the features of this
package are: - special-purpose implementations of Lists and Maps
for fast access

- adapter classes from Java1-style containers (arrays, enumerations)
to Java2-style collections

- methods to test or create typical set theory properties of
collections such as union, intersection, and closure