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)
Ensures that this collection contains the specified element (optional operation).int
add(E element, int occurrences)
Adds a number of occurrences of an element to this multiset.boolean
addAll(Collection<? extends E> elementsToAdd)
Adds all of the elements in the specified collection to this collection (optional operation).void
clear()
Removes all of the elements from this collection (optional operation).boolean
contains(Object element)
Returnstrue
if this collection 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 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(Object object)
Indicates whether some other object is "equal to" this one.int
hashCode()
Returns a hash code value for the object.boolean
isEmpty()
Returnstrue
if this collection contains no elements.Iterator<E>
iterator()
Returns an iterator over the elements contained in this collection.boolean
remove(Object element)
Removes a single instance of the specified element from this collection, if it is present (optional operation).int
remove(Object element, int occurrences)
Removes a number of occurrences of the specified element from this multiset.boolean
removeAll(Collection<?> elementsToRemove)
Removes all of this collection's elements that are also contained in the specified collection (optional operation).boolean
retainAll(Collection<?> elementsToRetain)
Retains only the elements in this collection that are contained in the specified collection (optional operation).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 number of elements in this collection.String
toString()
Returns a string representation of this collection.-
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, spliterator, stream, toArray, toArray, toArray
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Methods inherited from interface com.google.common.collect.Multiset
containsAll
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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:java.util.Collection
Returns the number of elements in this collection. If this collection contains more thanInteger.MAX_VALUE
elements, returnsInteger.MAX_VALUE
.
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count
public int count(@CheckForNull 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(@CheckForNull 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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clear
public void clear()
Description copied from class:java.util.AbstractCollection
Removes all of the elements from this collection (optional operation). The collection will be empty after this method returns.- Specified by:
clear
in interfaceCollection<E extends Enum<E>>
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iterator
public Iterator<E> iterator()
Description copied from class:java.util.AbstractCollection
Returns an iterator over the elements contained in this collection.- Specified by:
iterator
in interfaceCollection<E extends Enum<E>>
- Specified by:
iterator
in interfaceIterable<E extends Enum<E>>
- Specified by:
iterator
in interfaceMultiset<E extends Enum<E>>
- Specified by:
iterator
in classAbstractCollection<E extends Enum<E>>
- Returns:
- an iterator over the elements contained in this collection
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isEmpty
public boolean isEmpty()
Description copied from class:java.util.AbstractCollection
Returnstrue
if this collection contains no elements.- Specified by:
isEmpty
in interfaceCollection<E extends @Nullable Object>
- Overrides:
isEmpty
in classAbstractCollection<E extends @Nullable Object>
- Returns:
true
if this collection contains no elements
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contains
public boolean contains(@CheckForNull Object element)
Description copied from class:java.util.AbstractCollection
Returnstrue
if this collection contains the specified element. More formally, returnstrue
if and only if this collection contains at least one elemente
such thatObjects.equals(o, e)
.- 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
- element whose presence in this collection is to be tested- Returns:
true
if this collection contains the specified element
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add
@CanIgnoreReturnValue public final boolean add(E element)
Description copied from class:java.util.AbstractCollection
Ensures that this collection contains the specified element (optional operation). Returnstrue
if this collection changed as a result of the call. (Returnsfalse
if this collection does not permit duplicates and already contains the specified element.)Collections that support this operation may place limitations on what elements may be added to this collection. In particular, some collections will refuse to add
null
elements, and others will impose restrictions on the type of elements that may be added. Collection classes should clearly specify in their documentation any restrictions on what elements may be added.If a collection refuses to add a particular element for any reason other than that it already contains the element, it must throw an exception (rather than returning
false
). This preserves the invariant that a collection always contains the specified element after this call returns.- 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
- element whose presence in this collection is to be ensured- Returns:
true
if this collection changed as a result of the call
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remove
@CanIgnoreReturnValue public final boolean remove(@CheckForNull Object element)
Description copied from class:java.util.AbstractCollection
Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an elemente
such thatObjects.equals(o, e)
, if this collection contains one or more such elements. Returnstrue
if this collection contained the specified element (or equivalently, if this collection changed as a result of the call).- 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
- element to be removed from this collection, if present- Returns:
true
if an element was removed as a result of this call
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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)
Adds all of the elements in the specified collection to this collection (optional operation). The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified collection is this collection, and this collection is nonempty.)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>
- Parameters:
elementsToAdd
- collection containing elements to be added to this collection- Returns:
true
if this collection changed as a result of the call- See Also:
AbstractCollection.add(Object)
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removeAll
@CanIgnoreReturnValue public final boolean removeAll(Collection<?> elementsToRemove)
Description copied from class:java.util.AbstractCollection
Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.- 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>
- Parameters:
elementsToRemove
- collection containing elements to be removed from this collection- Returns:
true
if this collection changed as a result of the call- See Also:
AbstractCollection.remove(Object)
,AbstractCollection.contains(Object)
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retainAll
@CanIgnoreReturnValue public final boolean retainAll(Collection<?> elementsToRetain)
Description copied from class:java.util.AbstractCollection
Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.- 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>
- Parameters:
elementsToRetain
- collection containing elements to be retained in this collection- Returns:
true
if this collection changed as a result of the call- See Also:
AbstractCollection.remove(Object)
,AbstractCollection.contains(Object)
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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(@CheckForNull Object object)
Indicates whether some other object is "equal to" this one.The
equals
method implements an equivalence relation on non-null object references:- It is reflexive: for any non-null reference value
x
,x.equals(x)
should returntrue
. - It is symmetric: for any non-null reference values
x
andy
,x.equals(y)
should returntrue
if and only ify.equals(x)
returnstrue
. - It is transitive: for any non-null reference values
x
,y
, andz
, ifx.equals(y)
returnstrue
andy.equals(z)
returnstrue
, thenx.equals(z)
should returntrue
. - It is consistent: for any non-null reference values
x
andy
, multiple invocations ofx.equals(y)
consistently returntrue
or consistently returnfalse
, provided no information used inequals
comparisons on the objects is modified. - For any non-null reference value
x
,x.equals(null)
should returnfalse
.
The
equals
method for classObject
implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference valuesx
andy
, this method returnstrue
if and only ifx
andy
refer to the same object (x == y
has the valuetrue
).Note that it is generally necessary to override the
hashCode
method whenever this method is overridden, so as to maintain the general contract for thehashCode
method, which states that equal objects must have equal hash codes.This implementation returns
true
ifobject
is a multiset of the same size and if, for each element, the two multisets have the same count.- Specified by:
equals
in interfaceCollection<E extends @Nullable Object>
- Specified by:
equals
in interfaceMultiset<E extends @Nullable Object>
- Overrides:
equals
in classObject
- Parameters:
object
- the reference object with which to compare.- Returns:
true
if this object is the same as the obj argument;false
otherwise.- See Also:
Object.hashCode()
,HashMap
- It is reflexive: for any non-null reference value
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hashCode
public final int hashCode()
Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided byHashMap
.The general contract of
hashCode
is:- Whenever it is invoked on the same object more than once during
an execution of a Java application, the
hashCode
method must consistently return the same integer, provided no information used inequals
comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application. - If two objects are equal according to the
equals(Object)
method, then calling thehashCode
method on each of the two objects must produce the same integer result. - It is not required that if two objects are unequal
according to the
Object.equals(java.lang.Object)
method, then calling thehashCode
method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by class
Object
does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)This implementation returns the hash code of
Multiset.entrySet()
.- Specified by:
hashCode
in interfaceCollection<E extends @Nullable Object>
- Specified by:
hashCode
in interfaceMultiset<E extends @Nullable Object>
- Overrides:
hashCode
in classObject
- Returns:
- a hash code value for this object.
- See Also:
Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)
- Whenever it is invoked on the same object more than once during
an execution of a Java application, the
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toString
public final String toString()
Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"
). Adjacent elements are separated by the characters", "
(comma and space). Elements are converted to strings as byString.valueOf(Object)
.This implementation returns the result of invoking
toString
onMultiset.entrySet()
.
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