public final class ConcurrentHashMultiset<E>
extends java.util.AbstractCollection<E>
implements java.io.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(java.util.Collection<? extends E> elementsToAdd) |
void |
clear() |
boolean |
contains(java.lang.Object element)
Determines whether this multiset contains the specified element.
|
int |
count(java.lang.Object element)
Returns the number of occurrences of
element in this multiset. |
static <E> ConcurrentHashMultiset<E> |
create()
Creates a new, empty
ConcurrentHashMultiset using the default
initial capacity, load factor, and concurrency settings. |
static <E> ConcurrentHashMultiset<E> |
create(GenericMapMaker<? super E,? super java.lang.Number> mapMaker)
Creates a new, empty
ConcurrentHashMultiset using mapMaker
to construct the internal backing map. |
static <E> ConcurrentHashMultiset<E> |
create(java.lang.Iterable<? extends E> elements)
Creates a new
ConcurrentHashMultiset containing the specified elements, using
the default initial capacity, load factor, and concurrency settings. |
java.util.Set<E> |
elementSet()
Returns the set of distinct elements contained in this multiset.
|
java.util.Set<Multiset.Entry<E>> |
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(java.lang.Object object)
Compares the specified object with this multiset for equality.
|
int |
hashCode()
Returns the hash code for this multiset.
|
boolean |
isEmpty() |
java.util.Iterator<E> |
iterator() |
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 |
removeExactly(java.lang.Object element,
int occurrences)
Removes exactly the specified number of occurrences of
element, or makes no
change if this is not possible. |
boolean |
retainAll(java.util.Collection<?> elementsToRetain) |
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() |
java.lang.Object[] |
toArray() |
<T> T[] |
toArray(T[] array) |
java.lang.String |
toString() |
clone, finalize, getClass, notify, notifyAll, wait, wait, waitcontainsAllpublic static <E> ConcurrentHashMultiset<E> create()
ConcurrentHashMultiset using the default
initial capacity, load factor, and concurrency settings.public static <E> ConcurrentHashMultiset<E> create(java.lang.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(GenericMapMaker<? super E,? super java.lang.Number> 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.expireAfterAccess(long, java.util.concurrent.TimeUnit) makes sense (evict the entry that
was queried or updated longest ago), but MapMaker.expireAfterWrite(long, java.util.concurrent.TimeUnit) 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.
public int count(@Nullable
java.lang.Object element)
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.
size in interface java.util.Collection<E>public java.lang.Object[] toArray()
public <T> T[] toArray(T[] array)
public int add(E element, int occurrences)
add in interface Multiset<E>element - the element to addoccurrences - the number of occurrences to addjava.lang.IllegalArgumentException - if occurrences is negative, or if
the resulting amount would exceed Integer.MAX_VALUEpublic int remove(@Nullable
java.lang.Object element,
int occurrences)
remove in interface Multiset<E>element - the element whose occurrences should be removedoccurrences - the number of occurrences of the element to removejava.lang.IllegalArgumentException - if occurrences is negativepublic boolean removeExactly(@Nullable
java.lang.Object element,
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 removeoccurrences - the number of occurrences of element to removetrue if the removal was possible (including if occurrences is zero)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 implementationcount - the desired count of the element in this multisetelement in the multiset before this calljava.lang.IllegalArgumentException - if count is negativepublic 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 implementationexpectedOldCount - the expected present count of the element in this multisetnewCount - the desired count of the element in this multisettrue 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.java.lang.IllegalArgumentException - if expectedOldCount or newCount is negativepublic java.util.Set<Multiset.Entry<E>> entrySet()
MultisetMultiset.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 isEmpty()
isEmpty in interface java.util.Collection<E>public void clear()
clear in interface java.util.Collection<E>public boolean contains(@Nullable
java.lang.Object element)
MultisetThis method refines Collection.contains(java.lang.Object) to further specify that
it may not throw an exception in response to element being
null or of the wrong type.
public java.util.Iterator<E> iterator()
MultisetElements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.
public boolean add(@Nullable
E element)
MultisetThis 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.
add in interface java.util.Collection<E>add in interface Multiset<E>add in class java.util.AbstractCollection<E>element - the element to add one occurrence of; may be null only if
explicitly allowed by the implementationtrue always, since this call is required to modify the
multiset, unlike other Collection typespublic boolean remove(@Nullable
java.lang.Object element)
MultisetThis method refines Collection.remove(java.lang.Object) to further specify that it
may not throw an exception in response to element being null
or of the wrong type.
public boolean addAll(java.util.Collection<? extends E> elementsToAdd)
This implementation is highly efficient when elementsToAdd
is itself a Multiset.
addAll in interface java.util.Collection<E>addAll in class java.util.AbstractCollection<E>public boolean removeAll(java.util.Collection<?> elementsToRemove)
MultisetNote: 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.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 of elements
being null or of the wrong type.
public boolean retainAll(java.util.Collection<?> elementsToRetain)
MultisetNote: 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.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 of elements
being null or of the wrong type.
retainAll in interface java.util.Collection<E>retainAll in interface Multiset<E>retainAll in class java.util.AbstractCollection<E>Multisets.retainOccurrences(Multiset, Multiset)public java.util.Set<E> elementSet()
MultisetIf 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 boolean equals(@Nullable
java.lang.Object object)
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.entrySet().
public java.lang.String toString()
It is recommended, though not mandatory, that this method return the
result of invoking Multiset.toString() on the Multiset.entrySet(), yielding a
result such as [a x 3, c, d x 2, e].
This implementation returns the result of invoking toString on
Multiset.entrySet().