public final class ConcurrentHashMultiset<E> extends AbstractCollection<E> implements Serializable
Multiset
operations (exceptions where noted). Null elements are not supported.
See the Guava User Guide article on Multiset
.
Multiset.Entry <E>
Modifier and Type | Method and 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 the specified element to this multiset.
|
boolean |
addAll(Collection
|
void |
clear()
|
boolean |
contains(Object
Determines whether this multiset contains the specified element.
|
int |
count(Object
Returns the number of occurrences of
element in this multiset.
|
static <E> ConcurrentHashMultiset |
create()
Creates a new, empty
ConcurrentHashMultiset using the default initial capacity, load factor, and concurrency settings.
|
static <E> ConcurrentHashMultiset |
create(Iterable
Creates a new
ConcurrentHashMultiset containing the specified elements, using the default initial capacity, load factor, and concurrency settings.
|
static <E> ConcurrentHashMultiset |
create(MapMaker
Creates a new, empty
ConcurrentHashMultiset using
mapMaker to construct the internal backing map.
|
Set |
createEntrySet()
|
Set |
elementSet()
Returns the set of distinct elements contained in this multiset.
|
Set |
entrySet()
Returns a view of the contents of this multiset, grouped into
Multiset.Entry instances, each providing an element of the multiset and the count of that element.
|
boolean |
equals(Object
Compares the specified object with this multiset for equality.
|
int |
hashCode()
Returns the hash code for this multiset.
|
boolean |
isEmpty()
|
Iterator |
iterator()
|
boolean |
remove(Object
Removes a
single occurrence of the specified element from this multiset, if present.
|
int |
remove(Object
Removes a number of occurrences of the specified element from this multiset.
|
boolean |
removeAll(Collection
|
boolean |
removeExactly(Object
Removes exactly the specified number of occurrences of
element , or makes no change if this is not possible.
|
boolean |
retainAll(Collection
|
int |
setCount(E element, int count)
Adds or removes occurrences of
element such that the
count(java.lang.Object) of the element becomes
count .
|
boolean |
setCount(E element, int expectedOldCount, int newCount)
Sets the number of occurrences of
element to
newCount , but only if the count is currently
expectedOldCount .
|
int |
size()
|
Object |
toArray()
|
<T> T[] |
toArray(T[] array)
|
String |
toString()
|
containsAll
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
containsAll
parallelStream, removeIf, spliterator, stream
public static <E> ConcurrentHashMultiset<E> create()
ConcurrentHashMultiset
using the default initial capacity, load factor, and concurrency settings.
public static <E> ConcurrentHashMultiset<E> create(Iterable <? extends E> elements)
ConcurrentHashMultiset
containing the specified elements, using the default initial capacity, load factor, and concurrency settings.
This implementation is highly efficient when elements
is itself a Multiset
.
elements
- the elements that the multiset should contain
@Beta public static <E> ConcurrentHashMultiset<E> create(MapMaker mapMaker)
ConcurrentHashMultiset
using
mapMaker
to construct the internal backing map.
If this MapMaker
is configured to use entry eviction of any kind, this eviction applies to all occurrences of a given element as a single unit. However, most updates to the multiset do not count as map updates at all, since we're usually just mutating the value stored in the map, so MapMaker
makes sense (evict the entry that was queried or updated longest ago), but MapMaker
doesn't, because the eviction time is measured from when we saw the first occurrence of the object.
The returned multiset is serializable but any serialization caveats given in MapMaker
apply.
Finally, soft/weak values can be used but are not very useful: the values are created internally and not exposed externally, so no one else will have a strong reference to the values. Weak keys on the other hand can be useful in some scenarios.
GenericMapMaker
class) since 7.0)
public int count(Objectelement)
element
in this multiset.
public int size()
If the data in the multiset is modified by any other threads during this method, it is undefined which (if any) of these modifications will be reflected in the result.
public Object[] toArray()
public <T> T[] toArray(T[] array)
public int add(E element, int occurrences)
add
in interface
Multiset<E>
element
- the element to add
occurrences
- the number of occurrences to add
IllegalArgumentException
- if
occurrences
is negative, or if the resulting amount would exceed
Integer.MAX_VALUE
public int remove(Objectelement, int occurrences)
remove
in interface
Multiset<E>
element
- the element whose occurrences should be removed
occurrences
- the number of occurrences of the element to remove
IllegalArgumentException
- if
occurrences
is negative
public boolean removeExactly(Objectelement, int occurrences)
element
, or makes no change if this is not possible.
This method, in contrast to remove(Object, int)
, has no effect when the element count is smaller than occurrences
.
element
- the element to remove
occurrences
- the number of occurrences of
element
to remove
true
if the removal was possible (including if
occurrences
is zero)
IllegalArgumentException
- if
occurrences
is negative
public int setCount(E element, int count)
element
such that the
count(java.lang.Object)
of the element becomes
count
.
setCount
in interface
Multiset<E>
element
- the element to add or remove occurrences of; may be null only if explicitly allowed by the implementation
count
- the desired count of the element in this multiset
element
in the multiset before this call
IllegalArgumentException
- if
count
is negative
public boolean setCount(E element, int expectedOldCount, int newCount)
element
to
newCount
, but only if the count is currently
expectedOldCount
. If
element
does not appear in the multiset exactly
expectedOldCount
times, no changes will be made.
setCount
in interface
Multiset<E>
element
- the element to conditionally set the count of; may be null only if explicitly allowed by the implementation
expectedOldCount
- the expected present count of the element in this multiset
newCount
- the desired count of the element in this multiset
true
if the change was successful. This usually indicates that the multiset has been modified, but not always: in the case that
expectedOldCount == newCount
, the method will return
true
if the condition was met.
IllegalArgumentException
- if
expectedOldCount
or
newCount
is negative
public Set<Multiset .Entry <E>> createEntrySet()
public boolean isEmpty()
public void clear()
public boolean contains(Objectelement)
Multiset
This method refines Collection
to further specify that it may not throw an exception in response to element
being null or of the wrong type.
contains
in interface
Multiset<E>
contains
in interface
Collection<E>
contains
in class
AbstractCollection<E>
element
- the element to check for
true
if this multiset contains at least one occurrence of the element
public Iterator<E> iterator()
Multiset
Elements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.
public boolean add(E element)
Multiset
This method refines Collection
, 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.
add
in interface
Multiset<E>
add
in interface
Collection<E>
add
in class
AbstractCollection<E>
element
- the element to add one occurrence of; may be null only if explicitly allowed by the implementation
true
always, since this call is required to modify the multiset, unlike other
Collection
types
public boolean remove(Objectelement)
Multiset
This method refines Collection
to further specify that it may not throw an exception in response to element
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.
remove
in interface
Multiset<E>
remove
in interface
Collection<E>
remove
in class
AbstractCollection<E>
element
- the element to remove one occurrence of
true
if an occurrence was found and removed
public boolean addAll(Collection<? extends E> elementsToAdd)
This implementation is highly efficient when elementsToAdd
is itself a Multiset
.
public boolean removeAll(Collection<?> elementsToRemove)
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 in c
, see Multisets
.
This method refines Collection
to further specify that it may not throw an exception in response to any of elements
being null or of the wrong type.
public boolean retainAll(Collection<?> elementsToRetain)
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 in c
, see Multisets
.
This method refines Collection
to further specify that it may not throw an exception in response to any of elements
being null or of the wrong type.
retainAll
in interface
Multiset<E>
retainAll
in interface
Collection<E>
retainAll
in class
AbstractCollection<E>
Multisets.retainOccurrences(Multiset, Multiset)
public Set<E> elementSet()
Multiset
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()
.
elementSet
in interface
Multiset<E>
public Set<Multiset .Entry <E>> entrySet()
Multiset
Multiset.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 the
Multiset.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 the Entry
instances themselves don't even have methods for modification. See the specific implementation class for more details on how its entry set handles modifications.
public boolean equals(Objectobject)
true
if the given object is also a multiset and contains equal elements with equal counts, regardless of order.
This implementation returns true
if object
is a multiset of the same size and if, for each element, the two multisets have the same count.
public int hashCode()
((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
.
public StringtoString()
It is recommended, though not mandatory, that this method return the result of invoking Multiset
on the Multiset
, yielding a result such as [a x 3, c, d x 2, e]
.
This implementation returns the result of invoking toString
on Multiset
.