@GwtCompatible(serializable=true, emulated=true) public final class HashMultiset<E> extends AbstractCollection<E>
Multiset implementation backed by a HashMap.
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 an element to this multiset.
|
boolean |
addAll(Collection<? extends E> elementsToAdd) |
void |
clear() |
boolean |
contains(Object element)
Determines whether this multiset contains the specified element.
|
int |
count(Object element)
Returns the number of occurrences of an element in this multiset (the count of the element).
|
static <E> HashMultiset<E> |
create()
Creates a new, empty
HashMultiset using the default initial capacity. |
static <E> HashMultiset<E> |
create(int distinctElements)
Creates a new, empty
HashMultiset with the specified expected number of distinct elements. |
static <E> HashMultiset<E> |
create(Iterable<? extends E> elements)
Creates a new
HashMultiset containing the specified elements. |
Set<E> |
elementSet()
Returns the set of distinct elements contained in this multiset.
|
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(Object object)
Compares the specified object with this multiset for equality.
|
int |
hashCode()
Returns the hash code for this multiset.
|
boolean |
isEmpty() |
Iterator<E> |
iterator() |
boolean |
remove(Object element)
Removes a single occurrence of the specified element from this multiset, if present.
|
int |
remove(Object element,
int occurrences)
Removes a number of occurrences of the specified element from this multiset.
|
boolean |
removeAll(Collection<?> elementsToRemove) |
boolean |
retainAll(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 in
Multiset.setCount(Object, int), provided that the element has the expected current count. |
int |
size() |
String |
toString() |
containsAll, toArray, toArrayclone, finalize, getClass, notify, notifyAll, wait, wait, waitcontainsAllparallelStream, removeIf, spliterator, stream, toArray, toArraypublic static <E> HashMultiset<E> create()
Creates a new, empty HashMultiset using the default initial capacity.
public static <E> HashMultiset<E> create(int distinctElements)
Creates a new, empty HashMultiset with the specified expected number of distinct elements.
distinctElements - the expected number of distinct elementsIllegalArgumentException - if distinctElements is negativepublic static <E> HashMultiset<E> create(Iterable<? extends E> elements)
Creates a new HashMultiset containing the specified elements.
This implementation is highly efficient when elements is itself a Multiset.
elements - the elements that the multiset should containpublic 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. 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.
Invoking Multiset.Entry.getCount() on an entry in the returned
set always returns the current count of that element in the multiset, as
opposed to the count at the time the entry was retrieved.
public void clear()
clear in interface Collection<E>public int size()
size in interface Collection<E>public Iterator<E> iterator()
MultisetElements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.
public int count(@Nullable Object element)
MultisetReturns the number of occurrences of an element in this multiset (the count of the element). Note that for an Object.equals(java.lang.Object)-based multiset, this gives the same result as Collections.frequency(java.util.Collection<?>, java.lang.Object) (which would presumably perform more poorly).
Note: the utility method Iterables.frequency(java.lang.Iterable<?>, java.lang.Object) generalizes this operation; it correctly delegates to this method when dealing with a multiset, but it can also accept any other iterable type.
public int add(@Nullable E element, int occurrences)
Adds a number of occurrences of an element to this multiset. Note that if occurrences == 1, this method has the identical effect to Multiset.add(Object). This method is functionally equivalent (except in the case of overflow) to the call addAll(Collections.nCopies(element,
occurrences)), which would presumably perform much more poorly.
add in interface Multiset<E>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.IllegalArgumentException - if the call would result in more than
Integer.MAX_VALUE occurrences of element in this
multiset.public int remove(@Nullable Object element, int occurrences)
MultisetRemoves 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 if occurrences == 1, this is functionally equivalent to the call remove(element).
remove in interface Multiset<E>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.public int setCount(@Nullable E element, int count)
MultisetAdds or removes the necessary occurrences of an element such that the element attains the desired 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 multisetpublic boolean isEmpty()
isEmpty in interface Collection<E>isEmpty in class AbstractCollection<E>public boolean contains(@Nullable Object element)
MultisetDetermines 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 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 fortrue if this multiset contains at least one occurrence of the elementpublic boolean add(@Nullable E element)
MultisetAdds 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.
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 implementationtrue always, since this call is required to modify the multiset, unlike other Collection typespublic boolean remove(@Nullable Object element)
MultisetRemoves 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 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 oftrue if an occurrence was found and removedpublic boolean setCount(@Nullable E element, int oldCount, int newCount)
MultisetConditionally sets the count of an element to a new value, as described in Multiset.setCount(Object, int), provided that the element has the expected current count. If the current count is not oldCount, no change is made.
setCount in interface Multiset<E>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 multisettrue if the condition for modification was met. This implies that the multiset was indeed modified, unless oldCount == newCount.public 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()
MultisetReturns 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().
elementSet in interface Multiset<E>public boolean equals(@Nullable Object object)
Compares the specified object with this multiset for equality. Returns 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()
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().
public 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().