# Package org.apache.commons.collections4.set

This package contains implementations of the `Set`, `SortedSet` and `NavigableSet` interfaces.

See: Description

- Interface Summary
  Interface | Description
  --- | ---
  CompositeSet.SetMutator<E> | Define callbacks for mutation operations.

- Class Summary
  Class | Description
  --- | ---
  AbstractNavigableSetDecorator<E> | Decorates another `NavigableSet` to provide additional behaviour.
  AbstractSerializableSetDecorator<E> | Serializable subclass of AbstractSetDecorator.
  AbstractSetDecorator<E> | Decorates another `Set` to provide additional behaviour.
  AbstractSortedSetDecorator<E> | Decorates another `SortedSet` to provide additional behaviour.
  CompositeSet<E> | Decorates a set of other sets to provide a single unified view.
  ListOrderedSet<E> | Decorates another `Set` to ensure that the order of addition is retained and used by the iterator.
  MapBackedSet<E,V> | Decorates a `Map` to obtain `Set` behaviour.
  PredicatedNavigableSet<E> | Decorates another `NavigableSet` to validate that all additions match a specified predicate.
  PredicatedSet<E> | Decorates another `Set` to validate that all additions match a specified predicate.
  PredicatedSortedSet<E> | Decorates another `SortedSet` to validate that all additions match a specified predicate.
  TransformedNavigableSet<E> | Decorates another `NavigableSet` to transform objects that are added.
  TransformedSet<E> | Decorates another `Set` to transform objects that are added.
  TransformedSortedSet<E> | Decorates another `SortedSet` to transform objects that are added.
  UnmodifiableNavigableSet<E> | Decorates another `NavigableSet` to ensure it can't be altered.
  UnmodifiableSet<E> | Decorates another `Set` to ensure it can't be altered.
  UnmodifiableSortedSet<E> | Decorates another `SortedSet` to ensure it can't be altered.

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

This package contains implementations of the `Set`, `SortedSet` and `NavigableSet` interfaces.

The implementations are in the form of direct implementations and decorators. A decorator wraps another implementation of the interface to add some specific additional functionality.

The following implementations are provided in the package:

- CompositeSet - a set that combines multiple sets into one

The following decorators are provided in the package:

- Unmodifiable - ensures the collection cannot be altered
- Predicated - ensures that only elements that are valid according to a predicate can be added
- Transformed - transforms each element added
- ListOrdered - ensures that insertion order is retained
- MapBackedSet - a set formed by decorating a Map

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