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

All Methods Instance Methods Concrete Methods
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.
`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.lang.Iterable
forEach

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
  - 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)

Class ForwardingMap.StandardKeySet

Constructor Summary

Method Summary

Methods inherited from class java.util.AbstractSet

Methods inherited from class java.util.AbstractCollection

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

Constructor Detail

StandardKeySet

Method Detail

iterator

size

isEmpty

contains

remove

clear

removeAll

retainAll