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What are the main packages in Apache Commons Collections 4?

Commons Collections 4 organizes its classes under org.apache.commons.collections4 and a set of focused sub-packages rather than one large flat package.

bag - Bag implementations like HashBag and TreeBag
bidimap - DualHashBidiMap, DualTreeBidiMap, TreeBidiMap
map - LRUMap, ReferenceMap, MultiKeyMap, LinkedMap
multimap - ArrayListValuedHashMap, HashSetValuedHashMap
functors - concrete Predicate, Transformer, Closure, Factory implementations
iterators - LoopingIterator, FilterIterator, TransformIterator
comparators - ComparatorChain, FixedOrderComparator
trie - PatriciaTrie for prefix-based key lookups

Splitting the library this way keeps each concern isolated, so importing one feature set doesn't drag in unrelated classes.

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Which sub-package holds concrete Predicate, Transformer, and Closure classes? bidimap

✗ Try again if not.

trie

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functors

✓ Correct! Well done.

PatriciaTrie, used for prefix-based lookups, lives in which sub-package? trie

✓ Correct! Well done.

iterators

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map

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