||A DocIdSet built as applying "AND" operation to a list of other DocIdSet(s).
||A slightly different version of Lucene's original
SoftReferences instead of
WeakReferences in order to cache
||A Filter capable of chaining other filters, so that it's
possible to apply several filters on a Query.
||Helper class to apply some common optimizations when
several Filters are applied.
||Keep the most recently used Filters in the cache
The cache is at least as big as
Above this limit, Filters are kept as soft references