Class AbstractMultiset<E>
- java.lang.Object
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- java.util.AbstractCollection<E>
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- com.google.common.collect.AbstractMultiset<E>
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- All Implemented Interfaces:
Multiset<E>
,java.lang.Iterable<E>
,java.util.Collection<E>
- Direct Known Subclasses:
AbstractMapBasedMultiset
,AbstractSortedMultiset
,ConcurrentHashMultiset
,EnumMultiset
,Multimaps.Keys
,Multisets.ViewMultiset
abstract class AbstractMultiset<E> extends java.util.AbstractCollection<E> implements Multiset<E>
This class provides a skeletal implementation of theMultiset
interface. A new multiset implementation can be created easily by extending this class and implementing theMultiset.entrySet()
method, plus optionally overridingadd(Object, int)
andremove(Object, int)
to enable modifications to the multiset.The
Multiset.count(java.lang.Object)
andAbstractCollection.size()
implementations all iterate across the set returned byMultiset.entrySet()
, as do many methods acting on the set returned byelementSet()
. Override those methods for better performance.
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Nested Class Summary
Nested Classes Modifier and Type Class Description (package private) class
AbstractMultiset.ElementSet
(package private) class
AbstractMultiset.EntrySet
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Nested classes/interfaces inherited from interface com.google.common.collect.Multiset
Multiset.Entry<E>
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Field Summary
Fields Modifier and Type Field Description private java.util.Set<E>
elementSet
private java.util.Set<Multiset.Entry<E>>
entrySet
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Constructor Summary
Constructors Constructor Description AbstractMultiset()
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description boolean
add(E element)
Adds a single occurrence of the specified element to this multiset.int
add(E element, int occurrences)
Adds a number of occurrences of an element to this multiset.boolean
addAll(java.util.Collection<? extends E> elementsToAdd)
abstract void
clear()
boolean
contains(java.lang.Object element)
Determines whether this multiset contains the specified element.(package private) java.util.Set<E>
createElementSet()
Creates a new instance of this multiset's element set, which will be returned byelementSet()
.(package private) java.util.Set<Multiset.Entry<E>>
createEntrySet()
(package private) abstract int
distinctElements()
(package private) abstract java.util.Iterator<E>
elementIterator()
java.util.Set<E>
elementSet()
Returns the set of distinct elements contained in this multiset.(package private) abstract java.util.Iterator<Multiset.Entry<E>>
entryIterator()
java.util.Set<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.boolean
equals(java.lang.Object object)
Compares the specified object with this multiset for equality.int
hashCode()
Returns the hash code for this multiset.boolean
isEmpty()
boolean
remove(java.lang.Object element)
Removes a single occurrence of the specified element from this multiset, if present.int
remove(java.lang.Object element, int occurrences)
Removes a number of occurrences of the specified element from this multiset.boolean
removeAll(java.util.Collection<?> elementsToRemove)
boolean
retainAll(java.util.Collection<?> elementsToRetain)
int
setCount(E element, int count)
Adds or removes the necessary occurrences of an element such that the element attains the desired count.boolean
setCount(E element, int oldCount, int newCount)
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.java.lang.String
toString()
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Methods inherited from class java.util.AbstractCollection
containsAll, iterator, size, toArray, toArray
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArray, toArray, toArray
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Methods inherited from interface com.google.common.collect.Multiset
containsAll, count, forEach, forEachEntry, iterator, size, spliterator
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Field Detail
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elementSet
@CheckForNull private transient java.util.Set<E> elementSet
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entrySet
@CheckForNull private transient java.util.Set<Multiset.Entry<E>> entrySet
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Method Detail
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isEmpty
public boolean isEmpty()
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contains
public boolean contains(@CheckForNull java.lang.Object element)
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.
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add
public final boolean add(E element)
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 interfacejava.util.Collection<E>
- Specified by:
add
in interfaceMultiset<E>
- Overrides:
add
in classjava.util.AbstractCollection<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
public int add(E element, int occurrences)
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
public final boolean remove(@CheckForNull java.lang.Object element)
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.
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remove
public int remove(@CheckForNull java.lang.Object element, int occurrences)
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
public int setCount(E element, int count)
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
public boolean setCount(E element, int oldCount, int newCount)
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
public final boolean addAll(java.util.Collection<? extends E> elementsToAdd)
This implementation is highly efficient when
elementsToAdd
is itself aMultiset
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removeAll
public final boolean removeAll(java.util.Collection<?> elementsToRemove)
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.
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retainAll
public final boolean retainAll(java.util.Collection<?> elementsToRetain)
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.
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clear
public abstract void clear()
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elementSet
public java.util.Set<E> 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
java.util.Set<E> createElementSet()
Creates a new instance of this multiset's element set, which will be returned byelementSet()
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elementIterator
abstract java.util.Iterator<E> elementIterator()
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entrySet
public java.util.Set<Multiset.Entry<E>> 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.
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createEntrySet
java.util.Set<Multiset.Entry<E>> createEntrySet()
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entryIterator
abstract java.util.Iterator<Multiset.Entry<E>> entryIterator()
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distinctElements
abstract int distinctElements()
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equals
public final boolean equals(@CheckForNull java.lang.Object object)
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.
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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
public final java.lang.String 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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