MapBackedSet (Apache Commons Collections 4.0 API)

java.lang.Object
- org.apache.commons.collections4.set.MapBackedSet<E,V>

All Implemented Interfaces:

Serializable, Iterable<E>, Collection<E>, Set<E>
```
public final class MapBackedSet<E,V>
extends Object
implements Set<E>, 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:

3.1

Version:

$Id: MapBackedSet.html 972421 2015-11-14 20:00:04Z tn $

See Also:
Serialized Form

Method Summary

Methods
Modifier and Type	Method and Description
`boolean`	`add(E obj)`
`boolean`	`addAll(Collection<? extends E> coll)`
`void`	`clear()`
`boolean`	`contains(Object obj)`
`boolean`	`containsAll(Collection<?> coll)`
`boolean`	`equals(Object obj)`
`int`	`hashCode()`
`boolean`	`isEmpty()`
`Iterator<E>`	`iterator()`
`static <E,V> MapBackedSet<E,V>`	`mapBackedSet(Map<E,? super V> map)` Factory method to create a set from a map.
`static <E,V> MapBackedSet<E,V>`	`mapBackedSet(Map<E,? super V> map, V dummyValue)` Factory method to create a set from a map.
`boolean`	`remove(Object obj)`
`boolean`	`removeAll(Collection<?> coll)`
`boolean`	`retainAll(Collection<?> coll)`
`int`	`size()`
`Object[]`	`toArray()`
`<T> T[]`	`toArray(T[] array)`

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - mapBackedSet
```
public static <E,V> MapBackedSet<E,V> mapBackedSet(Map<E,? super V> map)
```
    Factory method to create a set from a map.
    
    Type Parameters:
    E - the element type
    V - the dummy value type in the map
    Parameters:
    map - the map to decorate, must not be null
    
    Returns:
    a new map backed set
    
    Throws:
    
    IllegalArgumentException - if set is null
    Since:
    
    4.0
  - mapBackedSet
```
public static <E,V> MapBackedSet<E,V> mapBackedSet(Map<E,? super V> map,
                                   V dummyValue)
```
    Factory method to create a set from a map.
    
    Type Parameters:
    E - the element type
    V - the dummy value type in the map
    Parameters:
    map - the map to decorate, must not be null
    dummyValue - the dummy value to use
    
    Returns:
    a new map backed set
    
    Throws:
    
    IllegalArgumentException - if map is null
    Since:
    
    4.0
  - size
```
public int size()
```
    Specified by:
    
    size in interface Collection<E>
    
    Specified by:
    
    size in interface Set<E>
  - isEmpty
```
public boolean isEmpty()
```
    Specified by:
    
    isEmpty in interface Collection<E>
    
    Specified by:
    
    isEmpty in interface Set<E>
  - iterator
```
public Iterator<E> iterator()
```
    Specified by:
    
    iterator in interface Iterable<E>
    
    Specified by:
    
    iterator in interface Collection<E>
    
    Specified by:
    
    iterator in interface Set<E>
  - contains
```
public boolean contains(Object obj)
```
    Specified by:
    
    contains in interface Collection<E>
    
    Specified by:
    
    contains in interface Set<E>
  - containsAll
```
public boolean containsAll(Collection<?> coll)
```
    Specified by:
    
    containsAll in interface Collection<E>
    
    Specified by:
    
    containsAll in interface Set<E>
  - add
```
public boolean add(E obj)
```
    Specified by:
    
    add in interface Collection<E>
    
    Specified by:
    
    add in interface Set<E>
  - addAll
```
public boolean addAll(Collection<? extends E> coll)
```
    Specified by:
    
    addAll in interface Collection<E>
    
    Specified by:
    
    addAll in interface Set<E>
  - remove
```
public boolean remove(Object obj)
```
    Specified by:
    
    remove in interface Collection<E>
    
    Specified by:
    
    remove in interface Set<E>
  - removeAll
```
public boolean removeAll(Collection<?> coll)
```
    Specified by:
    
    removeAll in interface Collection<E>
    
    Specified by:
    
    removeAll in interface Set<E>
  - retainAll
```
public boolean retainAll(Collection<?> coll)
```
    Specified by:
    
    retainAll in interface Collection<E>
    
    Specified by:
    
    retainAll in interface Set<E>
  - clear
```
public void clear()
```
    Specified by:
    
    clear in interface Collection<E>
    
    Specified by:
    
    clear in interface Set<E>
  - toArray
```
public Object[] toArray()
```
    Specified by:
    
    toArray in interface Collection<E>
    
    Specified by:
    
    toArray in interface Set<E>
  - toArray
```
public <T> T[] toArray(T[] array)
```
    Specified by:
    
    toArray in interface Collection<E>
    
    Specified by:
    
    toArray in interface Set<E>
  - equals
```
public boolean equals(Object obj)
```
    Specified by:
    
    equals in interface Collection<E>
    
    Specified by:
    
    equals in interface Set<E>
    
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Specified by:
    
    hashCode in interface Collection<E>
    
    Specified by:
    
    hashCode in interface Set<E>
    
    Overrides:
    
    hashCode in class Object

Class MapBackedSet<E,V>

Method Summary

Methods inherited from class java.lang.Object

Method Detail

mapBackedSet

mapBackedSet

size

isEmpty

iterator

contains

containsAll

add

addAll

remove

removeAll

retainAll

clear

toArray

toArray

equals

hashCode