java.util.AbstractCollection<E>
com.google.common.collect.HashMultiset<E>
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java.lang.Object
public final class HashMultiset<E>
Multiset implementation backed by a HashMap.
| 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 an 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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boolean |
containsAll(Collection<?> elements)
Returns true if this multiset contains at least one occurrence of
each element in the specified collection. |
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int |
count(Object element)
Returns the number of occurrences of an element in this multiset (the count of the element). |
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static
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create()
Creates a new, empty HashMultiset using the default initial
capacity. |
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static
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create(int distinctElements)
Creates a new, empty HashMultiset with the specified expected
number of distinct elements. |
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static
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create(Iterable<? extends E> elements)
Creates a new HashMultiset containing the specified elements. |
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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 |
retainAll(Collection<?> elementsToRetain)
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int |
setCount(E element,
int count)
Adds or removes the necessary occurrences of an element such that the element attains the desired count. |
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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. |
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int |
size()
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String |
toString()
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| Methods inherited from class java.util.AbstractCollection |
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toArray, toArray |
| Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface java.util.Collection |
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toArray, toArray |
| Method Detail |
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public static <E> HashMultiset<E> create()
HashMultiset using the default initial
capacity.
public static <E> HashMultiset<E> create(int distinctElements)
HashMultiset with the specified expected
number of distinct elements.
distinctElements - the expected number of distinct elements
IllegalArgumentException - if distinctElements is negativepublic static <E> HashMultiset<E> create(Iterable<? extends E> elements)
HashMultiset containing the specified elements.
elements - the elements that the multiset should containpublic Set<Multiset.Entry<E>> entrySet()
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.
entrySet in interface Multiset<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.
iterator in interface Multiset<E>iterator in interface Iterable<E>iterator in interface Collection<E>
public int count(@Nullable
Object element)
MultisetObject.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.
count in interface Multiset<E>element - the element to count occurrences of
public int add(@Nullable
E element,
int occurrences)
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)
Multisetoccurrences == 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(E element,
int count)
Multiset
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
public boolean isEmpty()
isEmpty in interface Collection<E>isEmpty in class AbstractCollection<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 element
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 typespublic boolean remove(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 removed
public boolean setCount(E element,
int oldCount,
int newCount)
MultisetMultiset.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 multiset
true if the condition for modification was met. This
implies that the multiset was indeed modified, unless
oldCount == newCount.public boolean containsAll(Collection<?> elements)
Multisettrue if this multiset contains at least one occurrence of
each element in the specified collection.
This method refines Collection.containsAll(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.
Note: this method does not take into account the occurrence
count of an element in the two collections; it may still return true even if elements contains several occurrences of an element
and this multiset contains only one. This is no different than any other
collection type like List, but it may be unexpected to the user of
a multiset.
containsAll in interface Multiset<E>containsAll in interface Collection<E>containsAll in class AbstractCollection<E>elements - the collection of elements to be checked for containment in
this multiset
true if this multiset contains at least one occurrence of
each element contained in elementspublic boolean addAll(Collection<? extends E> elementsToAdd)
addAll in interface Collection<E>addAll in class AbstractCollection<E>public boolean removeAll(Collection<?> elementsToRemove)
MultisetThis 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)
MultisetThis 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>public void clear()
clear in interface Collection<E>clear in class AbstractCollection<E>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 other 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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