Class EnumMultiset<E extends Enum<E>>
- java.lang.Object
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- java.util.AbstractCollection<E>
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- com.google.common.collect.EnumMultiset<E>
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- All Implemented Interfaces:
Multiset<E>
,Serializable
,Iterable<E>
,Collection<E>
@GwtCompatible(emulated=true) public final class EnumMultiset<E extends Enum<E>> extends AbstractCollection<E> implements Serializable
Multiset implementation specialized for enum elements, supporting all single-element operations in O(1).See the Guava User Guide article on
Multiset
.- Since:
- 2.0
- Author:
- Jared Levy
- See Also:
- Serialized Form
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Nested Class Summary
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Nested classes/interfaces inherited from interface com.google.common.collect.Multiset
Multiset.Entry<E extends @Nullable Object>
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method 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(@Nullable Object element)
Determines whether this multiset contains the specified element.int
count(@Nullable Object element)
Returns the number of occurrences of an element in this multiset (the count of the element).static <E extends Enum<E>>
EnumMultiset<E>create(Class<E> type)
Creates an emptyEnumMultiset
.static <E extends Enum<E>>
EnumMultiset<E>create(Iterable<E> elements)
Creates a newEnumMultiset
containing the specified elements.static <E extends Enum<E>>
EnumMultiset<E>create(Iterable<E> elements, Class<E> type)
Returns a newEnumMultiset
instance containing the given 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 intoMultiset.Entry
instances, each providing an element of the multiset and the count of that element.boolean
equals(@Nullable Object object)
Compares the specified object with this multiset for equality.void
forEachEntry(ObjIntConsumer<? super E> action)
Runs the specified action for each distinct element in this multiset, and the number of occurrences of that element.int
hashCode()
Returns the hash code for this multiset.boolean
isEmpty()
Iterator<E>
iterator()
boolean
remove(@Nullable Object element)
Removes a single occurrence of the specified element from this multiset, if present.int
remove(@Nullable 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 inMultiset.setCount(Object, int)
, provided that the element has the expected current count.int
size()
Returns the total number of all occurrences of all elements in this multiset.String
toString()
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Methods inherited from class java.util.AbstractCollection
containsAll, toArray, toArray
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArray, toArray, toArray
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Methods inherited from interface com.google.common.collect.Multiset
containsAll, forEach, spliterator
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Method Detail
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create
public static <E extends Enum<E>> EnumMultiset<E> create(Class<E> type)
Creates an emptyEnumMultiset
.
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create
public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements)
Creates a newEnumMultiset
containing the specified elements.This implementation is highly efficient when
elements
is itself aMultiset
.- Parameters:
elements
- the elements that the multiset should contain- Throws:
IllegalArgumentException
- ifelements
is empty
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create
public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements, Class<E> type)
Returns a newEnumMultiset
instance containing the given elements. Unlikecreate(Iterable)
, this method does not produce an exception on an empty iterable.- Since:
- 14.0
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size
public int size()
Description copied from interface:Multiset
Returns the total number of all occurrences of all elements in this multiset.Note: this method does not return the number of distinct elements in the multiset, which is given by
entrySet().size()
.
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count
public int count(@Nullable Object element)
Description copied from interface:Multiset
Returns the number of occurrences of an element in this multiset (the count of the element). Note that for anObject.equals(java.lang.Object)
-based multiset, this gives the same result asCollections.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.
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add
@CanIgnoreReturnValue public int add(E element, int occurrences)
Description copied from interface:Multiset
Adds a number of occurrences of an element to this multiset. Note that ifoccurrences == 1
, this method has the identical effect toMultiset.add(Object)
. This method is functionally equivalent (except in the case of overflow) to the calladdAll(Collections.nCopies(element, occurrences))
, which would presumably perform much more poorly.- Specified by:
add
in interfaceMultiset<E extends Enum<E>>
- Parameters:
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.- Returns:
- the count of the element before the operation; possibly zero
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remove
@CanIgnoreReturnValue public int remove(@Nullable Object element, int occurrences)
Description copied from interface:Multiset
Removes 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 ifoccurrences == 1
, this is functionally equivalent to the callremove(element)
.- Specified by:
remove
in interfaceMultiset<E extends Enum<E>>
- Parameters:
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.- Returns:
- the count of the element before the operation; possibly zero
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setCount
@CanIgnoreReturnValue public int setCount(E element, int count)
Description copied from interface:Multiset
Adds or removes the necessary occurrences of an element such that the element attains the desired count.- Specified by:
setCount
in interfaceMultiset<E extends Enum<E>>
- Parameters:
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- Returns:
- the count of the element before the operation; possibly zero
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forEachEntry
public void forEachEntry(ObjIntConsumer<? super E> action)
Description copied from interface:Multiset
Runs the specified action for each distinct element in this multiset, and the number of occurrences of that element. For someMultiset
implementations, this may be more efficient than iterating over theMultiset.entrySet()
either explicitly or withentrySet().forEach(action)
.- Specified by:
forEachEntry
in interfaceMultiset<E extends Enum<E>>
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iterator
public Iterator<E> iterator()
Description copied from interface:Multiset
Elements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.
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isEmpty
public boolean isEmpty()
- Specified by:
isEmpty
in interfaceCollection<E extends @Nullable Object>
- Overrides:
isEmpty
in classAbstractCollection<E extends @Nullable Object>
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contains
public boolean contains(@Nullable Object element)
Description copied from interface:Multiset
Determines 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 toelement
being null or of the wrong type.- Specified by:
contains
in interfaceCollection<E extends @Nullable Object>
- Specified by:
contains
in interfaceMultiset<E extends @Nullable Object>
- Overrides:
contains
in classAbstractCollection<E extends @Nullable Object>
- Parameters:
element
- the element to check for- Returns:
true
if this multiset contains at least one occurrence of the element
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add
@CanIgnoreReturnValue public final boolean add(E element)
Description copied from interface:Multiset
Adds 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.- Specified by:
add
in interfaceCollection<E extends @Nullable Object>
- Specified by:
add
in interfaceMultiset<E extends @Nullable Object>
- Overrides:
add
in classAbstractCollection<E extends @Nullable Object>
- Parameters:
element
- the element to add one occurrence of; may be null only if explicitly allowed by the implementation- Returns:
true
always, since this call is required to modify the multiset, unlike otherCollection
types
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remove
@CanIgnoreReturnValue public final boolean remove(@Nullable Object element)
Description copied from interface:Multiset
Removes 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 toelement
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.- Specified by:
remove
in interfaceCollection<E extends @Nullable Object>
- Specified by:
remove
in interfaceMultiset<E extends @Nullable Object>
- Overrides:
remove
in classAbstractCollection<E extends @Nullable Object>
- Parameters:
element
- the element to remove one occurrence of- Returns:
true
if an occurrence was found and removed
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setCount
@CanIgnoreReturnValue public boolean setCount(E element, int oldCount, int newCount)
Description copied from interface:Multiset
Conditionally sets the count of an element to a new value, as described inMultiset.setCount(Object, int)
, provided that the element has the expected current count. If the current count is notoldCount
, no change is made.- Specified by:
setCount
in interfaceMultiset<E extends @Nullable Object>
- Parameters:
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- Returns:
true
if the condition for modification was met. This implies that the multiset was indeed modified, unlessoldCount == newCount
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addAll
@CanIgnoreReturnValue public final boolean addAll(Collection<? extends E> elementsToAdd)
This implementation is highly efficient when
elementsToAdd
is itself aMultiset
.- Specified by:
addAll
in interfaceCollection<E extends @Nullable Object>
- Overrides:
addAll
in classAbstractCollection<E extends @Nullable Object>
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removeAll
@CanIgnoreReturnValue public final boolean removeAll(Collection<?> elementsToRemove)
Description copied from interface: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 inc
, seeMultisets.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 ofelements
being null or of the wrong type.- Specified by:
removeAll
in interfaceCollection<E extends @Nullable Object>
- Specified by:
removeAll
in interfaceMultiset<E extends @Nullable Object>
- Overrides:
removeAll
in classAbstractCollection<E extends @Nullable Object>
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retainAll
@CanIgnoreReturnValue public final boolean retainAll(Collection<?> elementsToRetain)
Description copied from interface: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 inc
, seeMultisets.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 ofelements
being null or of the wrong type.- Specified by:
retainAll
in interfaceCollection<E extends @Nullable Object>
- Specified by:
retainAll
in interfaceMultiset<E extends @Nullable Object>
- Overrides:
retainAll
in classAbstractCollection<E extends @Nullable Object>
- See Also:
Multisets.retainOccurrences(Multiset, Multiset)
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elementSet
public Set<E> elementSet()
Description copied from interface:Multiset
Returns 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()
.- Specified by:
elementSet
in interfaceMultiset<E extends @Nullable Object>
- Returns:
- a view of the set of distinct elements in this multiset
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entrySet
public Set<Multiset.Entry<E>> entrySet()
Description copied from interface:Multiset
Returns a view of the contents of this multiset, grouped intoMultiset.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 theMultiset.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 theEntry
instances themselves don't even have methods for modification. See the specific implementation class for more details on how its entry set handles modifications.
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equals
public final boolean equals(@Nullable Object object)
Compares the specified object with this multiset for equality. Returnstrue
if the given object is also a multiset and contains equal elements with equal counts, regardless of order.This implementation returns
true
ifobject
is a multiset of the same size and if, for each element, the two multisets have the same count.
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hashCode
public final 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()
.
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toString
public final String toString()
It is recommended, though not mandatory, that this method return the result of invoking
Multiset.toString()
on theMultiset.entrySet()
, yielding a result such as[a x 3, c, d x 2, e]
.This implementation returns the result of invoking
toString
onMultiset.entrySet()
.
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