Class ForwardingMultimap<K extends @Nullable Object,V extends @Nullable Object>
- java.lang.Object
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- com.google.common.collect.ForwardingObject
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- com.google.common.collect.ForwardingMultimap<K,V>
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- All Implemented Interfaces:
Multimap<K,V>
- Direct Known Subclasses:
ForwardingListMultimap
,ForwardingSetMultimap
@GwtCompatible public abstract class ForwardingMultimap<K extends @Nullable Object,V extends @Nullable Object> extends ForwardingObject implements Multimap<K,V>
A multimap which forwards all its method calls to another multimap. Subclasses should override one or more methods to modify the behavior of the backing multimap as desired per the decorator pattern.default
method warning: This class does not forward calls todefault
methods. Instead, it inherits their default implementations. When those implementations invoke methods, they invoke methods on theForwardingMultimap
.- Since:
- 2.0
- Author:
- Robert Konigsberg
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Constructor Summary
Constructors Modifier Constructor Description protected
ForwardingMultimap()
Constructor for use by subclasses.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description Map<K,Collection<V>>
asMap()
Returns a view of this multimap as aMap
from each distinct key to the nonempty collection of that key's associated values.void
clear()
Removes all key-value pairs from the multimap, leaving it empty.boolean
containsEntry(Object key, Object value)
Returnstrue
if this multimap contains at least one key-value pair with the keykey
and the valuevalue
.boolean
containsKey(Object key)
Returnstrue
if this multimap contains at least one key-value pair with the keykey
.boolean
containsValue(Object value)
Returnstrue
if this multimap contains at least one key-value pair with the valuevalue
.protected abstract Multimap<K,V>
delegate()
Returns the backing delegate instance that methods are forwarded to.Collection<Map.Entry<K,V>>
entries()
Returns a view collection of all key-value pairs contained in this multimap, asMap.Entry
instances.boolean
equals(Object object)
Indicates whether some other object is "equal to" this one.Collection<V>
get(K key)
Returns a view collection of the values associated withkey
in this multimap, if any.int
hashCode()
Returns a hash code value for the object.boolean
isEmpty()
Returnstrue
if this multimap contains no key-value pairs.Multiset<K>
keys()
Returns a view collection containing the key from each key-value pair in this multimap, without collapsing duplicates.Set<K>
keySet()
Returns a view collection of all distinct keys contained in this multimap.boolean
put(K key, V value)
Stores a key-value pair in this multimap.boolean
putAll(Multimap<? extends K,? extends V> multimap)
Stores all key-value pairs ofmultimap
in this multimap, in the order returned bymultimap.entries()
.boolean
putAll(K key, Iterable<? extends V> values)
Stores a key-value pair in this multimap for each ofvalues
, all using the same key,key
.boolean
remove(Object key, Object value)
Removes a single key-value pair with the keykey
and the valuevalue
from this multimap, if such exists.Collection<V>
removeAll(Object key)
Removes all values associated with the keykey
.Collection<V>
replaceValues(K key, Iterable<? extends V> values)
Stores a collection of values with the same key, replacing any existing values for that key.int
size()
Returns the number of key-value pairs in this multimap.Collection<V>
values()
Returns a view collection containing the value from each key-value pair contained in this multimap, without collapsing duplicates (sovalues().size() == size()
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Methods inherited from class com.google.common.collect.ForwardingObject
toString
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Constructor Detail
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ForwardingMultimap
protected ForwardingMultimap()
Constructor for use by subclasses.
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Method Detail
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delegate
protected abstract Multimap<K,V> delegate()
Description copied from class:ForwardingObject
Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such asForwardingSet.delegate()
. Concrete subclasses override this method to supply the instance being decorated.- Specified by:
delegate
in classForwardingObject
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asMap
public Map<K,Collection<V>> asMap()
Description copied from interface:Multimap
Returns a view of this multimap as aMap
from each distinct key to the nonempty collection of that key's associated values. Note thatthis.asMap().get(k)
is equivalent tothis.get(k)
only whenk
is a key contained in the multimap; otherwise it returnsnull
as opposed to an empty collection.Changes to the returned map or the collections that serve as its values will update the underlying multimap, and vice versa. The map does not support
put
orputAll
, nor do its entries supportsetValue
.
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clear
public void clear()
Description copied from interface:Multimap
Removes all key-value pairs from the multimap, leaving it empty.
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containsEntry
public boolean containsEntry(@CheckForNull Object key, @CheckForNull Object value)
Description copied from interface:Multimap
Returnstrue
if this multimap contains at least one key-value pair with the keykey
and the valuevalue
.
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containsKey
public boolean containsKey(@CheckForNull Object key)
Description copied from interface:Multimap
Returnstrue
if this multimap contains at least one key-value pair with the keykey
.
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containsValue
public boolean containsValue(@CheckForNull Object value)
Description copied from interface:Multimap
Returnstrue
if this multimap contains at least one key-value pair with the valuevalue
.
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entries
public Collection<Map.Entry<K,V>> entries()
Description copied from interface:Multimap
Returns a view collection of all key-value pairs contained in this multimap, asMap.Entry
instances.Changes to the returned collection or the entries it contains will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.
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get
public Collection<V> get(K key)
Description copied from interface:Multimap
Returns a view collection of the values associated withkey
in this multimap, if any. Note that whencontainsKey(key)
is false, this returns an empty collection, notnull
.Changes to the returned collection will update the underlying multimap, and vice versa.
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isEmpty
public boolean isEmpty()
Description copied from interface:Multimap
Returnstrue
if this multimap contains no key-value pairs. Equivalent tosize() == 0
, but can in some cases be more efficient.
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keys
public Multiset<K> keys()
Description copied from interface:Multimap
Returns a view collection containing the key from each key-value pair in this multimap, without collapsing duplicates. This collection has the same size as this multimap, andkeys().count(k) == get(k).size()
for allk
.Changes to the returned multiset will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.
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keySet
public Set<K> keySet()
Description copied from interface:Multimap
Returns a view collection of all distinct keys contained in this multimap. Note that the key set contains a key if and only if this multimap maps that key to at least one value.Changes to the returned set will update the underlying multimap, and vice versa. However, adding to the returned set is not possible.
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put
@CanIgnoreReturnValue public boolean put(K key, V value)
Description copied from interface:Multimap
Stores a key-value pair in this multimap.Some multimap implementations allow duplicate key-value pairs, in which case
put
always adds a new key-value pair and increases the multimap size by 1. Other implementations prohibit duplicates, and storing a key-value pair that's already in the multimap has no effect.
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putAll
@CanIgnoreReturnValue public boolean putAll(K key, Iterable<? extends V> values)
Description copied from interface:Multimap
Stores a key-value pair in this multimap for each ofvalues
, all using the same key,key
. Equivalent to (but expected to be more efficient than):for (V value : values) { put(key, value); }
In particular, this is a no-op if
values
is empty.
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putAll
@CanIgnoreReturnValue public boolean putAll(Multimap<? extends K,? extends V> multimap)
Description copied from interface:Multimap
Stores all key-value pairs ofmultimap
in this multimap, in the order returned bymultimap.entries()
.
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remove
@CanIgnoreReturnValue public boolean remove(@CheckForNull Object key, @CheckForNull Object value)
Description copied from interface:Multimap
Removes a single key-value pair with the keykey
and the valuevalue
from this multimap, if such exists. If multiple key-value pairs in the multimap fit this description, which one is removed is unspecified.
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removeAll
@CanIgnoreReturnValue public Collection<V> removeAll(@CheckForNull Object key)
Description copied from interface:Multimap
Removes all values associated with the keykey
.Once this method returns,
key
will not be mapped to any values, so it will not appear inMultimap.keySet()
,Multimap.asMap()
, or any other views.
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replaceValues
@CanIgnoreReturnValue public Collection<V> replaceValues(K key, Iterable<? extends V> values)
Description copied from interface:Multimap
Stores a collection of values with the same key, replacing any existing values for that key.If
values
is empty, this is equivalent toremoveAll(key)
.- Specified by:
replaceValues
in interfaceMultimap<K extends @Nullable Object,V extends @Nullable Object>
- Returns:
- the collection of replaced values, or an empty collection if no values were previously associated with the key. The collection may be modifiable, but updating it will have no effect on the multimap.
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size
public int size()
Description copied from interface:Multimap
Returns the number of key-value pairs in this multimap.Note: this method does not return the number of distinct keys in the multimap, which is given by
keySet().size()
orasMap().size()
. See the opening section of theMultimap
class documentation for clarification.
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values
public Collection<V> values()
Description copied from interface:Multimap
Returns a view collection containing the value from each key-value pair contained in this multimap, without collapsing duplicates (sovalues().size() == size()
).Changes to the returned collection will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.
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equals
public boolean equals(@CheckForNull Object object)
Description copied from class:java.lang.Object
Indicates whether some other object is "equal to" this one.The
equals
method implements an equivalence relation on non-null object references:- It is reflexive: for any non-null reference value
x
,x.equals(x)
should returntrue
. - It is symmetric: for any non-null reference values
x
andy
,x.equals(y)
should returntrue
if and only ify.equals(x)
returnstrue
. - It is transitive: for any non-null reference values
x
,y
, andz
, ifx.equals(y)
returnstrue
andy.equals(z)
returnstrue
, thenx.equals(z)
should returntrue
. - It is consistent: for any non-null reference values
x
andy
, multiple invocations ofx.equals(y)
consistently returntrue
or consistently returnfalse
, provided no information used inequals
comparisons on the objects is modified. - For any non-null reference value
x
,x.equals(null)
should returnfalse
.
The
equals
method for classObject
implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference valuesx
andy
, this method returnstrue
if and only ifx
andy
refer to the same object (x == y
has the valuetrue
).Note that it is generally necessary to override the
hashCode
method whenever this method is overridden, so as to maintain the general contract for thehashCode
method, which states that equal objects must have equal hash codes.- Specified by:
equals
in interfaceMultimap<K extends @Nullable Object,V extends @Nullable Object>
- Overrides:
equals
in classObject
- Parameters:
object
- the reference object with which to compare.- Returns:
true
if this object is the same as the obj argument;false
otherwise.- See Also:
Object.hashCode()
,HashMap
- It is reflexive: for any non-null reference value
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hashCode
public int hashCode()
Description copied from class:java.lang.Object
Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided byHashMap
.The general contract of
hashCode
is:- Whenever it is invoked on the same object more than once during
an execution of a Java application, the
hashCode
method must consistently return the same integer, provided no information used inequals
comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application. - If two objects are equal according to the
equals(Object)
method, then calling thehashCode
method on each of the two objects must produce the same integer result. - It is not required that if two objects are unequal
according to the
Object.equals(java.lang.Object)
method, then calling thehashCode
method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by class
Object
does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.) - Whenever it is invoked on the same object more than once during
an execution of a Java application, the
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