Package org.apache.commons.collections4.bag
This package contains implementations of the 
Bag and
 SortedBag interfaces.
 A bag stores an object and a count of the number of occurrences of the object.
 The following implementations are provided in the package:
- HashBag - implementation that uses a HashMap to store the data
 - TreeBag - implementation that uses a TreeMap to store the data
 
The following decorators are provided in the package:
- Synchronized - synchronizes method access for multi-threaded environments
 - Unmodifiable - ensures the bag cannot be altered
 - Predicated - ensures that only elements that are valid according to a predicate can be added
 - Transformed - transforms each element added to the bag
 - Collection - ensures compliance with the java.util.Collection contract
 
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Class Summary Class Description AbstractBagDecorator<E> Decorates anotherBagto provide additional behaviour.AbstractMapBag<E> Abstract implementation of theBaginterface to simplify the creation of subclass implementations.AbstractSortedBagDecorator<E> Decorates anotherSortedBagto provide additional behaviour.CollectionBag<E> Decorates anotherBagto comply with the Collection contract.CollectionSortedBag<E> Decorates anotherSortedBagto comply with the Collection contract.HashBag<E> ImplementsBag, using aHashMapto provide the data storage.PredicatedBag<E> Decorates anotherBagto validate that additions match a specified predicate.PredicatedSortedBag<E> Decorates anotherSortedBagto validate that additions match a specified predicate.SynchronizedBag<E> Decorates anotherBagto synchronize its behaviour for a multi-threaded environment.SynchronizedSortedBag<E> Decorates anotherSortedBagto synchronize its behaviour for a multi-threaded environment.TransformedBag<E> Decorates anotherBagto transform objects that are added.TransformedSortedBag<E> Decorates anotherSortedBagto transform objects that are added.TreeBag<E> ImplementsSortedBag, using aTreeMapto provide the data storage.UnmodifiableBag<E> Decorates anotherBagto ensure it can't be altered.UnmodifiableSortedBag<E> Decorates anotherSortedBagto ensure it can't be altered.