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 to Java2-style collections. - methods to test or create typical set-theory properties of collections such as union, intersection, and closure.