org.apache.commons.collections.set

## Class MapBackedSet

- java.lang.Object
- - org.apache.commons.collections.set.MapBackedSet

- All Implemented Interfaces:
    Serializable, Iterable, Collection, Set

      public final class MapBackedSet
      extends Object
      implements Set, Serializable

  Decorates a `Map` to obtain `Set` behaviour.

  This class is used to create a `Set` with the same properties as the key set of any map. Thus, a ReferenceSet can be created by wrapping a `ReferenceMap` in an instance of this class.

  Most map implementation can be used to create a set by passing in dummy values. Exceptions include `BidiMap` implementations, as they require unique values.

  Since:
    Commons Collections 3.1
  Version:
    $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
  Author:
    Stephen Colebourne
  See Also:
    Serialized Form

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Object` | `dummyValue` The dummyValue to use
    `protected Map` | `map` The map being used as the backing store

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `add(Object obj)`
    `boolean` | `addAll(Collection coll)`
    `void` | `clear()`
    `boolean` | `contains(Object obj)`
    `boolean` | `containsAll(Collection coll)`
    `static Set` | `decorate(Map map)` Factory method to create a set from a map.
    `static Set` | `decorate(Map map, Object dummyValue)` Factory method to create a set from a map.
    `boolean` | `equals(Object obj)`
    `int` | `hashCode()`
    `boolean` | `isEmpty()`
    `Iterator` | `iterator()`
    `boolean` | `remove(Object obj)`
    `boolean` | `removeAll(Collection coll)`
    `boolean` | `retainAll(Collection coll)`
    `int` | `size()`
    `Object[]` | `toArray()`
    `Object[]` | `toArray(Object[] array)`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### map

          protected final Map map

      The map being used as the backing store

    - #### dummyValue

          protected final Object dummyValue

      The dummyValue to use

  - ### Method Detail

    - #### decorate

          public static Set decorate(Map map)

      Factory method to create a set from a map.
      Parameters:
        `map` - the map to decorate, must not be null
      Throws:
        `IllegalArgumentException` - if set is null

    - #### decorate

          public static Set decorate(Map map,
                     Object dummyValue)

      Factory method to create a set from a map.
      Parameters:
        `map` - the map to decorate, must not be null
        `dummyValue` - the dummy value to use
      Throws:
        `IllegalArgumentException` - if map is null

    - #### size

          public int size()

      Specified by:
        `size` in interface `Collection`
      Specified by:
        `size` in interface `Set`

    - #### isEmpty

          public boolean isEmpty()

      Specified by:
        `isEmpty` in interface `Collection`
      Specified by:
        `isEmpty` in interface `Set`

    - #### iterator

          public Iterator iterator()

      Specified by:
        `iterator` in interface `Iterable`
      Specified by:
        `iterator` in interface `Collection`
      Specified by:
        `iterator` in interface `Set`

    - #### contains

          public boolean contains(Object obj)

      Specified by:
        `contains` in interface `Collection`
      Specified by:
        `contains` in interface `Set`

    - #### containsAll

          public boolean containsAll(Collection coll)

      Specified by:
        `containsAll` in interface `Collection`
      Specified by:
        `containsAll` in interface `Set`

    - #### add

          public boolean add(Object obj)

      Specified by:
        `add` in interface `Collection`
      Specified by:
        `add` in interface `Set`

    - #### addAll

          public boolean addAll(Collection coll)

      Specified by:
        `addAll` in interface `Collection`
      Specified by:
        `addAll` in interface `Set`

    - #### remove

          public boolean remove(Object obj)

      Specified by:
        `remove` in interface `Collection`
      Specified by:
        `remove` in interface `Set`

    - #### removeAll

          public boolean removeAll(Collection coll)

      Specified by:
        `removeAll` in interface `Collection`
      Specified by:
        `removeAll` in interface `Set`

    - #### retainAll

          public boolean retainAll(Collection coll)

      Specified by:
        `retainAll` in interface `Collection`
      Specified by:
        `retainAll` in interface `Set`

    - #### clear

          public void clear()

      Specified by:
        `clear` in interface `Collection`
      Specified by:
        `clear` in interface `Set`

    - #### toArray

          public Object[] toArray()

      Specified by:
        `toArray` in interface `Collection`
      Specified by:
        `toArray` in interface `Set`

    - #### toArray

          public Object[] toArray(Object[] array)

      Specified by:
        `toArray` in interface `Collection`
      Specified by:
        `toArray` in interface `Set`

    - #### equals

          public boolean equals(Object obj)

      Specified by:
        `equals` in interface `Collection`
      Specified by:
        `equals` in interface `Set`
      Overrides:
        `equals` in class `Object`

    - #### hashCode

          public int hashCode()

      Specified by:
        `hashCode` in interface `Collection`
      Specified by:
        `hashCode` in interface `Set`
      Overrides:
        `hashCode` in class `Object`

Copyright © 2001–2015 The Apache Software Foundation. All rights reserved.