Class ConcurrentHashMultiset<E>
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- <E>
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- com.google.common.collect.ConcurrentHashMultiset<E>
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- All Implemented Interfaces:
,
<E>
,<E>
@GwtIncompatible public final class ConcurrentHashMultiset<E> extends <E> implements
A multiset that supports concurrent modifications and that provides atomic versions of mostMultiset
operations (exceptions where noted). Null elements are not supported.See the Guava User Guide article on .
- Since:
- 2.0
- Author:
- Cliff L. Biffle, mike nonemacher
- 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>
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description boolean
E element)
Ensures that this collection contains the specified element (optional operation).int
add(E element, int occurrences)
Adds a number of occurrences of the specified element to this multiset.boolean
<? 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
element)
Returnstrue
if this collection contains the specified element.int
element)
Returns the number of occurrences ofelement
in this multiset.static <E> ConcurrentHashMultiset<E>
create()
Creates a new, emptyConcurrentHashMultiset
using the default initial capacity, load factor, and concurrency settings.static <E> ConcurrentHashMultiset<E>
<? extends E> elements)
Creates a newConcurrentHashMultiset
containing the specified elements, using the default initial capacity, load factor, and concurrency settings.static <E> ConcurrentHashMultiset<E>
<E,> countMap)
Creates a new, emptyConcurrentHashMultiset
usingcountMap
as the internal backing map.<Multiset.Entry<E>>
createEntrySet()
Deprecated.Internal method, useMultiset.entrySet()
.<E>
elementSet()
Returns the set of distinct elements contained in this multiset.<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
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.<E>
iterator()
Returns an iterator over the elements contained in this collection.boolean
element)
Removes a single instance of the specified element from this collection, if it is present (optional operation).int
element, int occurrences)
Removes a number of occurrences of the specified element from this multiset.boolean
<?> elementsToRemove)
Removes all of this collection's elements that are also contained in the specified collection (optional operation).boolean
element, int occurrences)
Removes exactly the specified number of occurrences ofelement
, or makes no change if this is not possible.boolean
<?> 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 occurrences ofelement
such that thecount(java.lang.Object)
of the element becomescount
.boolean
setCount(E element, int expectedOldCount, int newCount)
Sets the number of occurrences ofelement
tonewCount
, but only if the count is currentlyexpectedOldCount
.int
size()
Returns the number of elements in this collection.[]
toArray()
Returns an array containing all of the elements in this collection.<T> T[]
toArray(T[] array)
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.toString()
Returns a string representation of this collection.-
Methods inherited from interface com.google.common.collect.Multiset
containsAll, forEach, forEachEntry, spliterator
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Method Detail
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create
public static <E> ConcurrentHashMultiset<E> create()
Creates a new, emptyConcurrentHashMultiset
using the default initial capacity, load factor, and concurrency settings.
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create
public static <E> <? extends E> elements)
Creates a newConcurrentHashMultiset
containing the specified elements, using the default initial capacity, load factor, and concurrency settings.This implementation is highly efficient when
elements
is itself aMultiset
.- Parameters:
elements
- the elements that the multiset should contain
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create
@Beta public static <E> <E,> countMap)
Creates a new, emptyConcurrentHashMultiset
usingcountMap
as the internal backing map.This instance will assume ownership of
countMap
, and other code should not maintain references to the map or modify it in any way.The returned multiset is serializable if the input map is.
- Parameters:
countMap
- backing map for storing the elements in the multiset and their counts. It must be empty.- Throws:
- if
countMap
is not empty- Since:
- 20.0
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count
public int element)
Returns the number of occurrences ofelement
in this multiset.
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size
public int size()
Returns the number of elements in this collection. If this collection contains more thanInteger.MAX_VALUE
elements, returnsInteger.MAX_VALUE
.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.
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toArray
public [] toArray()
Description copied from class:Returns an array containing all of the elements in this collection. If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. The returned array's isObject
.The returned array will be "safe" in that no references to it are maintained by this collection. (In other words, this method must allocate a new array even if this collection is backed by an array). The caller is thus free to modify the returned array.
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toArray
public <T> T[] toArray(T[] array)
Description copied from class:Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this collection.If this collection fits in the specified array with room to spare (i.e., the array has more elements than this collection), the element in the array immediately following the end of the collection is set to
null
. (This is useful in determining the length of this collection only if the caller knows that this collection does not contain anynull
elements.)If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
- Specified by:
in interface
<E>
- Overrides:
in class
<E>
- Type Parameters:
T
- the component type of the array to contain the collection- Parameters:
array
- the array into which the elements of this collection are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.- Returns:
- an array containing all of the elements in this collection
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add
public int add(E element, int occurrences)
Adds a number of occurrences of the specified element to this multiset.
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remove
public int element, int occurrences)
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.
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removeExactly
public boolean element, int occurrences)
Removes exactly the specified number of occurrences ofelement
, 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 thanoccurrences
.- Parameters:
element
- the element to removeoccurrences
- the number of occurrences ofelement
to remove- Returns:
true
if the removal was possible (including ifoccurrences
is zero)- Throws:
- if
occurrences
is negative
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setCount
public int setCount(E element, int count)
Adds or removes occurrences ofelement
such that thecount(java.lang.Object)
of the element becomescount
.- Specified by:
setCount
in interfaceMultiset<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
element
in the multiset before this call - Throws:
- if
count
is negative
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setCount
public boolean setCount(E element, int expectedOldCount, int newCount)
Sets the number of occurrences ofelement
tonewCount
, but only if the count is currentlyexpectedOldCount
. Ifelement
does not appear in the multiset exactlyexpectedOldCount
times, no changes will be made.- Specified by:
setCount
in interfaceMultiset<E>
- Parameters:
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- Returns:
true
if the change was successful. This usually indicates that the multiset has been modified, but not always: in the case thatexpectedOldCount == newCount
, the method will returntrue
if the condition was met.- Throws:
- if
expectedOldCount
ornewCount
is negative
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createEntrySet
public <Multiset.Entry<E>> createEntrySet()
Deprecated.Internal method, useMultiset.entrySet()
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isEmpty
public boolean isEmpty()
Description copied from class:Returnstrue
if this collection contains no elements.- Specified by:
in interface
<E>
- Returns:
true
if this collection contains no elements
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iterator
public <E> iterator()
Description copied from class:Returns an iterator over the elements contained in this collection.
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clear
public void clear()
Description copied from class:Removes all of the elements from this collection (optional operation). The collection will be empty after this method returns.- Specified by:
in interface
<E>
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contains
public boolean contains( element)
Description copied from class: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)
.
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add
public final boolean add( E element)
Description copied from class: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.
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remove
public final boolean remove( element)
Description copied from class: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).
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addAll
public final boolean addAll(<? 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:
in interface
<E>
- Overrides:
in class
<E>
- 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:
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removeAll
public final boolean removeAll(<?> elementsToRemove)
Description copied from class: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.
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retainAll
public final boolean retainAll(<?> elementsToRetain)
Description copied from class: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.
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elementSet
public <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>
- Returns:
- a view of the set of distinct elements in this multiset
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entrySet
public <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( 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. - 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 by .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
method, then calling the
hashCode
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()
. - 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 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 by .This implementation returns the result of invoking
toString
onMultiset.entrySet()
.
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