Package com.google.common.collect

Class ForwardingMap.StandardKeySet

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractSet<E>

com.google.common.collect.ForwardingMap.StandardKeySet

All Implemented Interfaces:

Iterable<K>, Collection<K>, Set<K>

Enclosing class:

ForwardingMap<K extends @Nullable Object,V extends @Nullable Object>

@Beta
protected class ForwardingMap.StandardKeySet
extends AbstractSet<E>

A sensible implementation of Map.keySet() in terms of the following methods: ForwardingMap.clear(), ForwardingMap.containsKey(java.lang.Object), ForwardingMap.isEmpty(), ForwardingMap.remove(java.lang.Object), ForwardingMap.size(), and the Set.iterator() method of ForwardingMap.entrySet(). In many cases, you may wish to override ForwardingMap.keySet() to forward to this implementation or a subclass thereof.

Since:

10.0

Constructor Summary

Constructors

Constructor	Description
StandardKeySet()	Constructor for use by subclasses.

Method Summary

Modifier and Type	Method	Description
void	clear()	Removes all of the elements from this collection (optional operation).
boolean	contains(Object o)	Returns true if this collection contains the specified element.
void	forEach(Consumer<? super K> action)	Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.
boolean	isEmpty()	Returns true if this collection contains no elements.
Iterator<K>	iterator()	Returns an iterator over the elements contained in this collection.
boolean	remove(Object o)	Removes a single instance of the specified element from this collection, if it is present (optional operation).
boolean	removeAll(Collection<?> c)	Removes from this set all of its elements that are contained in the specified collection (optional operation).
boolean	retainAll(Collection<?> c)	Retains only the elements in this collection that are contained in the specified collection (optional operation).
int	size()	Returns the number of elements in this collection.

Methods inherited from class java.util.AbstractSet

equals, hashCode

Methods inherited from class java.util.AbstractCollection

add, addAll, containsAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream, toArray

Methods inherited from interface java.util.Set

add, addAll, containsAll, spliterator, toArray, toArray

Constructor Detail

StandardKeySet

public StandardKeySet()

Constructor for use by subclasses.

Method Detail

iterator

public Iterator<K> iterator()

Description copied from class: java.util.AbstractCollection

Returns an iterator over the elements contained in this collection.

Specified by:

iterator in interface Collection<K extends @Nullable Object>

Specified by:

iterator in interface Iterable<K extends @Nullable Object>

Specified by:

iterator in interface Set<K extends @Nullable Object>

Specified by:

iterator in class AbstractCollection<K extends @Nullable Object>

Returns:

an iterator over the elements contained in this collection

forEach

public void forEach(Consumer<? super K> action)

Description copied from interface: java.lang.Iterable

Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception. Actions are performed in the order of iteration, if that order is specified. Exceptions thrown by the action are relayed to the caller.

The behavior of this method is unspecified if the action performs side-effects that modify the underlying source of elements, unless an overriding class has specified a concurrent modification policy.

Parameters:

action - The action to be performed for each element

size

public int size()

Description copied from interface: java.util.Collection

Returns the number of elements in this collection. If this collection contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Specified by:

size in interface Collection<K extends @Nullable Object>

Specified by:

size in interface Set<K extends @Nullable Object>

Specified by:

size in class AbstractCollection<K extends @Nullable Object>

Returns:

the number of elements in this collection

isEmpty

public boolean isEmpty()

Description copied from class: java.util.AbstractCollection

Returns true if this collection contains no elements.

Specified by:

isEmpty in interface Collection<K extends @Nullable Object>

Specified by:

isEmpty in interface Set<K extends @Nullable Object>

Overrides:

isEmpty in class AbstractCollection<K extends @Nullable Object>

Returns:

true if this collection contains no elements

contains

public boolean contains(@CheckForNull
                        Object o)

Description copied from class: java.util.AbstractCollection

Returns true if this collection contains the specified element. More formally, returns true if and only if this collection contains at least one element e such that Objects.equals(o, e).

Specified by:

contains in interface Collection<K extends @Nullable Object>

Specified by:

contains in interface Set<K extends @Nullable Object>

Overrides:

contains in class AbstractCollection<K extends @Nullable Object>

Parameters:

o - element whose presence in this collection is to be tested

Returns:

true if this collection contains the specified element

remove

public boolean remove(@CheckForNull
                      Object o)

Description copied from class: java.util.AbstractCollection

Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an element e such that Objects.equals(o, e), if this collection contains one or more such elements. Returns true if this collection contained the specified element (or equivalently, if this collection changed as a result of the call).

Specified by:

remove in interface Collection<K extends @Nullable Object>

Specified by:

remove in interface Set<K extends @Nullable Object>

Overrides:

remove in class AbstractCollection<K extends @Nullable Object>

Parameters:

o - element to be removed from this collection, if present

Returns:

true if an element was removed as a result of this call

clear

public void clear()

Description copied from class: java.util.AbstractCollection

Removes all of the elements from this collection (optional operation). The collection will be empty after this method returns.

Specified by:

clear in interface Collection<K extends @Nullable Object>

Specified by:

clear in interface Set<K extends @Nullable Object>

Overrides:

clear in class AbstractCollection<K extends @Nullable Object>

removeAll

public boolean removeAll(Collection<?> c)

Description copied from class: java.util.AbstractSet

Removes from this set all of its elements that are contained in the specified collection (optional operation). If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets.

This implementation determines which is the smaller of this set and the specified collection, by invoking the size method on each. If this set has fewer elements, then the implementation iterates over this set, checking each element returned by the iterator in turn to see if it is contained in the specified collection. If it is so contained, it is removed from this set with the iterator's remove method. If the specified collection has fewer elements, then the implementation iterates over the specified collection, removing from this set each element returned by the iterator, using this set's remove method.

Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method.

Specified by:

removeAll in interface Collection<E extends @Nullable Object>

Specified by:

removeAll in interface Set<E extends @Nullable Object>

Overrides:

removeAll in class AbstractSet<E extends @Nullable Object>

Parameters:

c - collection containing elements to be removed from this set

Returns:

true if this set changed as a result of the call

See Also:

AbstractCollection.remove(Object), AbstractCollection.contains(Object)

retainAll

public boolean retainAll(Collection<?> c)

Description copied from class: java.util.AbstractCollection

Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.

Specified by:

retainAll in interface Collection<E extends @Nullable Object>

Specified by:

retainAll in interface Set<E extends @Nullable Object>

Overrides:

retainAll in class AbstractCollection<E extends @Nullable Object>

Parameters:

c - collection containing elements to be retained in this collection

Returns:

true if this collection changed as a result of the call

See Also:

AbstractCollection.remove(Object), AbstractCollection.contains(Object)