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 Description

protected Object dummyValue
The dummyValue to use

protected Map map
The map being used as the backing store

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	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

Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArray

Methods inherited from interface java.lang.Iterable
forEach

Methods inherited from interface java.util.Set
spliterator

- 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 Collection
    
    Specified by:
    
    iterator in interface Iterable
    
    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

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

Class MapBackedSet

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Collection

Methods inherited from interface java.lang.Iterable

Methods inherited from interface java.util.Set

Field Detail

map

dummyValue

Method Detail

decorate

decorate

size

isEmpty

iterator

contains

containsAll

add

addAll

remove

removeAll

retainAll

clear

toArray

toArray

equals

hashCode