java.util.AbstractCollection<E>
com.google.common.collect.ConcurrentHashMultiset<E>
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java.lang.Object
public final class ConcurrentHashMultiset<E>
A multiset that supports concurrent modifications and that provides atomic versions of most
Multiset operations (exceptions where noted). Null elements are not supported.
See the Guava User Guide article on
Multiset.
| Nested Class Summary |
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| Nested classes/interfaces inherited from interface com.google.common.collect.Multiset |
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Multiset.Entry<E> |
| Method Summary | ||
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boolean |
add(E element)
Adds a single occurrence of the specified element to this multiset. |
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int |
add(E element,
int occurrences)
Adds a number of occurrences of the specified element to this multiset. |
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boolean |
addAll(Collection<? extends E> elementsToAdd)
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void |
clear()
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boolean |
contains(Object element)
Determines whether this multiset contains the specified element. |
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int |
count(Object element)
Returns the number of occurrences of element in this multiset. |
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static
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create()
Creates a new, empty ConcurrentHashMultiset using the default
initial capacity, load factor, and concurrency settings. |
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static
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create(GenericMapMaker<? super E,? super Number> mapMaker)
Creates a new, empty ConcurrentHashMultiset using mapMaker
to construct the internal backing map. |
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static
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create(Iterable<? extends E> elements)
Creates a new ConcurrentHashMultiset containing the specified elements, using
the default initial capacity, load factor, and concurrency settings. |
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Set<E> |
elementSet()
Returns the set of distinct elements contained in this multiset. |
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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. |
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boolean |
equals(Object object)
Compares the specified object with this multiset for equality. |
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int |
hashCode()
Returns the hash code for this multiset. |
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boolean |
isEmpty()
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Iterator<E> |
iterator()
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boolean |
remove(Object element)
Removes a single occurrence of the specified element from this multiset, if present. |
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int |
remove(Object element,
int occurrences)
Removes a number of occurrences of the specified element from this multiset. |
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boolean |
removeAll(Collection<?> elementsToRemove)
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boolean |
removeExactly(Object element,
int occurrences)
Removes exactly the specified number of occurrences of element, or makes no
change if this is not possible. |
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boolean |
retainAll(Collection<?> elementsToRetain)
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int |
setCount(E element,
int count)
Adds or removes occurrences of element such that the count(java.lang.Object) of the
element becomes count. |
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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. |
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int |
size()
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Object[] |
toArray()
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toArray(T[] array)
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String |
toString()
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| Methods inherited from class java.util.AbstractCollection |
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containsAll |
| Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface com.google.common.collect.Multiset |
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containsAll |
| Method Detail |
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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(GenericMapMaker<? super E,? super 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
Object element)
element in this multiset.
count in interface Multiset<E>element - the element to look for
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 Collection<E>public Object[] toArray()
toArray in interface Collection<E>toArray in class AbstractCollection<E>public <T> T[] toArray(T[] array)
toArray in interface Collection<E>toArray in class AbstractCollection<E>
public int add(E element,
int occurrences)
add in interface Multiset<E>element - the element to addoccurrences - the number of occurrences to add
IllegalArgumentException - if occurrences is negative, or if
the resulting amount would exceed Integer.MAX_VALUE
public int remove(@Nullable
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 remove
IllegalArgumentException - if occurrences is negative
public boolean removeExactly(@Nullable
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 remove
true 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 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 implementationexpectedOldCount - the expected present count of the element in this multisetnewCount - 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 negativepublic 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.
entrySet in interface Multiset<E>public boolean isEmpty()
isEmpty in interface Collection<E>public void clear()
clear in interface Collection<E>
public boolean contains(@Nullable
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.
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 elementpublic Iterator<E> iterator()
MultisetElements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.
iterator in interface Multiset<E>iterator in interface Iterable<E>iterator in interface Collection<E>iterator in class AbstractCollection<E>
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 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(@Nullable
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.
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 removedpublic boolean addAll(Collection<? extends E> elementsToAdd)
This implementation is highly efficient when elementsToAdd
is itself a Multiset.
addAll in interface Collection<E>addAll in class AbstractCollection<E>public boolean removeAll(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.
removeAll in interface Multiset<E>removeAll in interface Collection<E>removeAll in class AbstractCollection<E>public boolean retainAll(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 Multiset<E>retainAll in interface Collection<E>retainAll in class AbstractCollection<E>Multisets.retainOccurrences(Multiset, Multiset)public 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
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.
equals in interface Multiset<E>equals in interface Collection<E>equals in class Objectpublic 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().
hashCode in interface Multiset<E>hashCode in interface Collection<E>hashCode in class Objectpublic 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().
toString in interface Multiset<E>toString in class AbstractCollection<E>
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