# Package org.apache.commons.collections4.multiset

This package contains implementations of the `MultiSet` interface.

See: Description

- Class Summary
  Class | Description
  --- | ---
  AbstractMapMultiSet<E> | Abstract implementation of the `MultiSet` interface to simplify the creation of subclass implementations.
  AbstractMapMultiSet.EntrySetIterator<E> | Inner class EntrySetIterator.
  AbstractMapMultiSet.MultiSetEntry<E> | Inner class MultiSetEntry.
  AbstractMapMultiSet.MutableInteger | Mutable integer class for storing the data.
  AbstractMapMultiSet.UniqueSetIterator<E> | Inner class UniqueSetIterator.
  AbstractMultiSet<E> | Abstract implementation of the `MultiSet` interface to simplify the creation of subclass implementations.
  AbstractMultiSet.AbstractEntry<E> | Inner class AbstractEntry.
  AbstractMultiSet.EntrySet<E> | Inner class EntrySet.
  AbstractMultiSet.UniqueSet<E> | Inner class UniqueSet.
  AbstractMultiSetDecorator<E> | Decorates another `MultSet` to provide additional behaviour.
  HashMultiSet<E> | Implements `MultiSet`, using a `HashMap` to provide the data storage.
  PredicatedMultiSet<E> | Decorates another `MultiSet` to validate that additions match a specified predicate.
  SynchronizedMultiSet<E> | Decorates another `MultiSet` to synchronize its behaviour for a multi-threaded environment.
  UnmodifiableMultiSet<E> | Decorates another `MultiSet` to ensure it can't be altered.

## Package org.apache.commons.collections4.multiset Description

This package contains implementations of the `MultiSet` interface. A multiset stores an object and a count of the number of occurrences of the object.

The following implementations are provided in the package:

- HashMultiSet - implementation that uses a HashMap to store the data

The following decorators are provided in the package:

- Predicated - ensures that only elements that are valid according to a predicate can be added
- Synchronized - synchronizes method access for multi-threaded environments
- Unmodifiable - ensures the multiset cannot be altered

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