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:

java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>, java.util.Set<E>

public final class MapBackedSet<E,V>
extends java.lang.Object
implements java.util.Set<E>, java.io.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

See Also:

Serialized Form

Method Summary

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

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Set

spliterator

Methods inherited from interface java.util.Collection

parallelStream, stream

Methods inherited from interface java.lang.Iterable

forEach

Method Detail

mapBackedSet

public static <E,V> MapBackedSet<E,V> mapBackedSet(java.util.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:

java.lang.NullPointerException - if map is null

Since:

4.0

mapBackedSet

public static <E,V> MapBackedSet<E,V> mapBackedSet(java.util.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:

java.lang.NullPointerException - if map is null

Since:

4.0

size

public int size()

Specified by:

size in interface java.util.Collection<E>

Specified by:

size in interface java.util.Set<E>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Collection<E>

Specified by:

isEmpty in interface java.util.Set<E>

iterator

public java.util.Iterator<E> iterator()

Specified by:

iterator in interface java.lang.Iterable<E>

Specified by:

iterator in interface java.util.Collection<E>

Specified by:

iterator in interface java.util.Set<E>

contains

public boolean contains(java.lang.Object obj)

Specified by:

contains in interface java.util.Collection<E>

Specified by:

contains in interface java.util.Set<E>

containsAll

public boolean containsAll(java.util.Collection<?> coll)

Specified by:

containsAll in interface java.util.Collection<E>

Specified by:

containsAll in interface java.util.Set<E>

add

public boolean add(E obj)

Specified by:

add in interface java.util.Collection<E>

Specified by:

add in interface java.util.Set<E>

addAll

public boolean addAll(java.util.Collection<? extends E> coll)

Specified by:

addAll in interface java.util.Collection<E>

Specified by:

addAll in interface java.util.Set<E>

remove

public boolean remove(java.lang.Object obj)

Specified by:

remove in interface java.util.Collection<E>

Specified by:

remove in interface java.util.Set<E>

removeIf

public boolean removeIf(java.util.function.Predicate<? super E> filter)

Specified by:

removeIf in interface java.util.Collection<E>

Since:

4.4

removeAll

public boolean removeAll(java.util.Collection<?> coll)

Specified by:

removeAll in interface java.util.Collection<E>

Specified by:

removeAll in interface java.util.Set<E>

retainAll

public boolean retainAll(java.util.Collection<?> coll)

Specified by:

retainAll in interface java.util.Collection<E>

Specified by:

retainAll in interface java.util.Set<E>

clear

public void clear()

Specified by:

clear in interface java.util.Collection<E>

Specified by:

clear in interface java.util.Set<E>

toArray

public java.lang.Object[] toArray()

Specified by:

toArray in interface java.util.Collection<E>

Specified by:

toArray in interface java.util.Set<E>

toArray

public <T> T[] toArray(T[] array)

Specified by:

toArray in interface java.util.Collection<E>

Specified by:

toArray in interface java.util.Set<E>

equals

public boolean equals(java.lang.Object obj)

Specified by:

equals in interface java.util.Collection<E>

Specified by:

equals in interface java.util.Set<E>

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Specified by:

hashCode in interface java.util.Collection<E>

Specified by:

hashCode in interface java.util.Set<E>

Overrides:

hashCode in class java.lang.Object