Class AbstractMultiset<E>
- All Implemented Interfaces:
Multiset<E>
,Iterable<E>
,Collection<E>
- Direct Known Subclasses:
AbstractMapBasedMultiset
,AbstractSortedMultiset
,ConcurrentHashMultiset
,EnumMultiset
,Multimaps.Keys
,Multisets.ViewMultiset
Multiset
interface. A new multiset
implementation can be created easily by extending this class and implementing the Multiset.entrySet()
method, plus optionally overriding add(Object, int)
and remove(Object, int)
to enable modifications to the multiset.
The Multiset.count(java.lang.Object)
and AbstractCollection.size()
implementations all iterate across the set returned by
Multiset.entrySet()
, as do many methods acting on the set returned by elementSet()
. Override those methods for better performance.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescription(package private) class
(package private) class
Nested classes/interfaces inherited from interface com.google.common.collect.Multiset
Multiset.Entry<E>
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Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionfinal boolean
Adds a single occurrence of the specified element to this multiset.int
Adds a number of occurrences of an element to this multiset.final boolean
addAll
(Collection<? extends E> elementsToAdd) abstract void
clear()
boolean
Determines whether this multiset contains the specified element.Creates a new instance of this multiset's element set, which will be returned byelementSet()
.(package private) Set
<Multiset.Entry<E>> (package private) abstract int
Returns the set of distinct elements contained in this multiset.(package private) abstract Iterator
<Multiset.Entry<E>> entrySet()
Returns a view of the contents of this multiset, grouped intoMultiset.Entry
instances, each providing an element of the multiset and the count of that element.final boolean
Compares the specified object with this multiset for equality.final int
hashCode()
Returns the hash code for this multiset.boolean
isEmpty()
final boolean
Removes a single occurrence of the specified element from this multiset, if present.int
Removes a number of occurrences of the specified element from this multiset.final boolean
removeAll
(Collection<?> elementsToRemove) final boolean
retainAll
(Collection<?> elementsToRetain) int
Adds or removes the necessary occurrences of an element such that the element attains the desired count.boolean
Conditionally sets the count of an element to a new value, as described inMultiset.setCount(Object, int)
, provided that the element has the expected current count.final String
toString()
Methods inherited from class java.util.AbstractCollection
containsAll, iterator, size, toArray, toArray
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, toArray, toArray
Methods inherited from interface com.google.common.collect.Multiset
containsAll, count, forEach, forEachEntry, iterator, size, spliterator
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Field Details
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elementSet
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entrySet
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Constructor Details
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AbstractMultiset
AbstractMultiset()
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Method Details
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isEmpty
public boolean isEmpty()- Specified by:
isEmpty
in interfaceCollection<E>
- Overrides:
isEmpty
in classAbstractCollection<E>
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contains
Description copied from interface:Multiset
Determines whether this multiset contains the specified element.This method refines
Collection.contains(java.lang.Object)
to further specify that it may not throw an exception in response toelement
being null or of the wrong type.- Specified by:
contains
in interfaceCollection<E>
- Specified by:
contains
in interfaceMultiset<E>
- Overrides:
contains
in classAbstractCollection<E>
- Parameters:
element
- the element to check for- Returns:
true
if this multiset contains at least one occurrence of the element
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add
Description copied from interface:Multiset
Adds a single occurrence of the specified element to this multiset.This method refines
Collection.add(E)
, which only ensures the presence of the element, to further specify that a successful call must always increment the count of the element, and the overall size of the collection, by one.To both add the element and obtain the previous count of that element, use
add
(element, 1)
instead.- Specified by:
add
in interfaceCollection<E>
- Specified by:
add
in interfaceMultiset<E>
- Overrides:
add
in classAbstractCollection<E>
- Parameters:
element
- the element to add one occurrence of; may be null only if explicitly allowed by the implementation- Returns:
true
always, since this call is required to modify the multiset, unlike otherCollection
types
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add
Description copied from interface:Multiset
Adds a number of occurrences of an element to this multiset. Note that ifoccurrences == 1
, this method has the identical effect toMultiset.add(Object)
. This method is functionally equivalent (except in the case of overflow) to the calladdAll(Collections.nCopies(element, occurrences))
, which would presumably perform much more poorly.- Specified by:
add
in interfaceMultiset<E>
- Parameters:
element
- the element to add occurrences of; may be null only if explicitly allowed by the implementationoccurrences
- the number of occurrences of the element to add. May be zero, in which case no change will be made.- Returns:
- the count of the element before the operation; possibly zero
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remove
Description copied from interface:Multiset
Removes a single occurrence of the specified element from this multiset, if present.This method refines
Collection.remove(java.lang.Object)
to further specify that it may not throw an exception in response toelement
being null or of the wrong type.To both remove the element and obtain the previous count of that element, use
remove
(element, 1)
instead.- Specified by:
remove
in interfaceCollection<E>
- Specified by:
remove
in interfaceMultiset<E>
- Overrides:
remove
in classAbstractCollection<E>
- Parameters:
element
- the element to remove one occurrence of- Returns:
true
if an occurrence was found and removed
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remove
Description copied from interface:Multiset
Removes a number of occurrences of the specified element from this multiset. If the multiset contains fewer than this number of occurrences to begin with, all occurrences will be removed. Note that ifoccurrences == 1
, this is functionally equivalent to the callremove(element)
.- Specified by:
remove
in interfaceMultiset<E>
- Parameters:
element
- the element to conditionally remove occurrences ofoccurrences
- the number of occurrences of the element to remove. May be zero, in which case no change will be made.- Returns:
- the count of the element before the operation; possibly zero
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setCount
Description copied from interface:Multiset
Adds or removes the necessary occurrences of an element such that the element attains the desired count.- Specified by:
setCount
in interfaceMultiset<E>
- Parameters:
element
- the element to add or remove occurrences of; may be null only if explicitly allowed by the implementationcount
- the desired count of the element in this multiset- Returns:
- the count of the element before the operation; possibly zero
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setCount
Description copied from interface:Multiset
Conditionally sets the count of an element to a new value, as described inMultiset.setCount(Object, int)
, provided that the element has the expected current count. If the current count is notoldCount
, no change is made.- Specified by:
setCount
in interfaceMultiset<E>
- Parameters:
element
- the element to conditionally set the count of; may be null only if explicitly allowed by the implementationoldCount
- the expected present count of the element in this multisetnewCount
- the desired count of the element in this multiset- Returns:
true
if the condition for modification was met. This implies that the multiset was indeed modified, unlessoldCount == newCount
.
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addAll
This implementation is highly efficient when
elementsToAdd
is itself aMultiset
.- Specified by:
addAll
in interfaceCollection<E>
- Overrides:
addAll
in classAbstractCollection<E>
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removeAll
Description copied from interface:Multiset
Note: This method ignores how often any element might appear in
c
, and only cares whether or not an element appears at all. If you wish to remove one occurrence in this multiset for every occurrence inc
, seeMultisets.removeOccurrences(Multiset, Multiset)
.This method refines
Collection.removeAll(java.util.Collection<?>)
to further specify that it may not throw an exception in response to any ofelements
being null or of the wrong type.- Specified by:
removeAll
in interfaceCollection<E>
- Specified by:
removeAll
in interfaceMultiset<E>
- Overrides:
removeAll
in classAbstractCollection<E>
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retainAll
Description copied from interface:Multiset
Note: This method ignores how often any element might appear in
c
, and only cares whether or not an element appears at all. If you wish to remove one occurrence in this multiset for every occurrence inc
, seeMultisets.retainOccurrences(Multiset, Multiset)
.This method refines
Collection.retainAll(java.util.Collection<?>)
to further specify that it may not throw an exception in response to any ofelements
being null or of the wrong type.- Specified by:
retainAll
in interfaceCollection<E>
- Specified by:
retainAll
in interfaceMultiset<E>
- Overrides:
retainAll
in classAbstractCollection<E>
- See Also:
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clear
public abstract void clear()- Specified by:
clear
in interfaceCollection<E>
- Overrides:
clear
in classAbstractCollection<E>
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elementSet
Description copied from interface:Multiset
Returns the set of distinct elements contained in this multiset. The element set is backed by the same data as the multiset, so any change to either is immediately reflected in the other. The order of the elements in the element set is unspecified.If the element set supports any removal operations, these necessarily cause all occurrences of the removed element(s) to be removed from the multiset. Implementations are not expected to support the add operations, although this is possible.
A common use for the element set is to find the number of distinct elements in the multiset:
elementSet().size()
.- Specified by:
elementSet
in interfaceMultiset<E>
- Returns:
- a view of the set of distinct elements in this multiset
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createElementSet
Creates a new instance of this multiset's element set, which will be returned byelementSet()
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elementIterator
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entrySet
Description copied from interface:Multiset
Returns a view of the contents of this multiset, grouped intoMultiset.Entry
instances, each providing an element of the multiset and the count of that element. This set contains exactly one entry for each distinct element in the multiset (thus it always has the same size as theMultiset.elementSet()
). The order of the elements in the element set is unspecified.The entry set is backed by the same data as the multiset, so any change to either is immediately reflected in the other. However, multiset changes may or may not be reflected in any
Entry
instances already retrieved from the entry set (this is implementation-dependent). Furthermore, implementations are not required to support modifications to the entry set at all, and theEntry
instances themselves don't even have methods for modification. See the specific implementation class for more details on how its entry set handles modifications. -
createEntrySet
Set<Multiset.Entry<E>> createEntrySet() -
entryIterator
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distinctElements
abstract int distinctElements() -
equals
Compares the specified object with this multiset for equality. Returnstrue
if the given object is also a multiset and contains equal elements with equal counts, regardless of order.This implementation returns
true
ifobject
is a multiset of the same size and if, for each element, the two multisets have the same count. -
hashCode
public final int hashCode()Returns the hash code for this multiset. This is defined as the sum of((element == null) ? 0 : element.hashCode()) ^ count(element)
over all distinct elements in the multiset. It follows that a multiset and its entry set always have the same hash code.
This implementation returns the hash code of
Multiset.entrySet()
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toString
It is recommended, though not mandatory, that this method return the result of invoking
Multiset.toString()
on theMultiset.entrySet()
, yielding a result such as[a x 3, c, d x 2, e]
.This implementation returns the result of invoking
toString
onMultiset.entrySet()
.
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