Package org.apache.commons.collections4.set

Class MapBackedSet<E,V>

java.lang.Object

org.apache.commons.collections4.set.MapBackedSet<E,V>

Type Parameters:

E - the type of the elements in this set

V - the dummy value type in this map

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 behavior.

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

See Also:

• Serialized Form

Method Summary

Modifier and Type	Method	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	removeIf(Predicate<? super E> filter)
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

Methods inherited from interface java.util.Collection

parallelStream, stream

Methods inherited from interface java.lang.Iterable

forEach

Methods inherited from interface java.util.Set

spliterator

Method Details

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:

NullPointerException - if map 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:

NullPointerException - if map is null

Since:

4.0

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>

clear

public void clear()

Specified by:

clear in interface Collection<E>

Specified by:

clear 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>

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

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 Collection<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator 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>

removeIf

public boolean removeIf(Predicate<? super E> filter)

Specified by:

removeIf in interface Collection<E>

Since:

4.4

retainAll

public boolean retainAll(Collection<?> coll)

Specified by:

retainAll in interface Collection<E>

Specified by:

retainAll in interface Set<E>

size

public int size()

Specified by:

size in interface Collection<E>

Specified by:

size 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>