Class ForwardingMultiset<E extends @Nullable Object>
- java.lang.Object
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- com.google.common.collect.ForwardingObject
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- com.google.common.collect.ForwardingCollection<E>
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- com.google.common.collect.ForwardingMultiset<E>
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- All Implemented Interfaces:
Multiset<E>,Iterable<E>,Collection<E>
- Direct Known Subclasses:
ForwardingSortedMultiset,ForwardingSortedMultiset.StandardDescendingMultiset
@GwtCompatible public abstract class ForwardingMultiset<E extends @Nullable Object> extends ForwardingCollection<E> implements Multiset<E>
A multiset which forwards all its method calls to another multiset. Subclasses should override one or more methods to modify the behavior of the backing multiset as desired per the decorator pattern.Warning: The methods of
ForwardingMultisetforward indiscriminately to the methods of the delegate. For example, overridingadd(Object, int)alone will not change the behavior ofForwardingCollection.add(Object), which can lead to unexpected behavior. In this case, you should overrideadd(Object)as well, either providing your own implementation, or delegating to the providedstandardAddmethod.defaultmethod warning: This class does not forward calls todefaultmethods. Instead, it inherits their default implementations. When those implementations invoke methods, they invoke methods on theForwardingMultiset.The
standardmethods and any collection views they return are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.- Since:
- 2.0
- Author:
- Kevin Bourrillion, Louis Wasserman
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected classForwardingMultiset.StandardElementSetA sensible implementation ofMultiset.elementSet()in terms of the following methods:ForwardingCollection.clear(),ForwardingCollection.contains(java.lang.Object),ForwardingCollection.containsAll(java.util.Collection<?>),count(java.lang.Object),ForwardingCollection.isEmpty(), theSet.size()andSet.iterator()methods ofentrySet(), andremove(Object, int).-
Nested classes/interfaces inherited from interface com.google.common.collect.Multiset
Multiset.Entry<E extends @Nullable Object>
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Constructor Summary
Constructors Modifier Constructor Description protectedForwardingMultiset()Constructor for use by subclasses.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description intadd(E element, int occurrences)Adds a number of occurrences of an element to this multiset.intcount(Object element)Returns the number of occurrences of an element in this multiset (the count of the element).protected abstract Multiset<E>delegate()Returns the backing delegate instance that methods are forwarded to.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.Entryinstances, each providing an element of the multiset and the count of that element.booleanequals(Object object)Indicates whether some other object is "equal to" this one.inthashCode()Returns a hash code value for the object.intremove(Object element, int occurrences)Removes a number of occurrences of the specified element from this multiset.intsetCount(E element, int count)Adds or removes the necessary occurrences of an element such that the element attains the desired count.booleansetCount(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.protected booleanstandardAdd(E element)A sensible definition ofForwardingCollection.add(Object)in terms ofadd(Object, int).protected booleanstandardAddAll(Collection<? extends E> elementsToAdd)A sensible definition ofForwardingCollection.addAll(Collection)in terms ofForwardingCollection.add(Object)andadd(Object, int).protected voidstandardClear()A sensible definition ofForwardingCollection.clear()in terms of theiteratormethod ofentrySet().protected booleanstandardContains(Object object)A sensible definition ofForwardingCollection.contains(java.lang.Object)in terms ofcount(java.lang.Object).protected intstandardCount(Object object)A sensible, albeit inefficient, definition ofcount(java.lang.Object)in terms ofentrySet().protected booleanstandardEquals(Object object)A sensible, albeit inefficient, definition ofequals(java.lang.Object)in terms ofentrySet().size()andcount(java.lang.Object).protected intstandardHashCode()A sensible definition ofhashCode()asentrySet().hashCode().protected Iterator<E>standardIterator()A sensible definition ofForwardingCollection.iterator()in terms ofentrySet()andForwardingCollection.remove(Object).protected booleanstandardRemove(Object element)A sensible definition ofForwardingCollection.remove(Object)in terms ofremove(Object, int).protected booleanstandardRemoveAll(Collection<?> elementsToRemove)A sensible definition ofForwardingCollection.removeAll(java.util.Collection<?>)in terms of theremoveAllmethod ofelementSet().protected booleanstandardRetainAll(Collection<?> elementsToRetain)A sensible definition ofForwardingCollection.retainAll(java.util.Collection<?>)in terms of theretainAllmethod ofelementSet().protected intstandardSetCount(E element, int count)A sensible definition ofsetCount(Object, int)in terms ofcount(Object),add(Object, int), andremove(Object, int).protected booleanstandardSetCount(E element, int oldCount, int newCount)A sensible definition ofsetCount(Object, int, int)in terms ofcount(Object)andsetCount(Object, int).protected intstandardSize()A sensible, albeit inefficient, definition ofForwardingCollection.size()in terms ofentrySet().protected StringstandardToString()A sensible definition ofForwardingObject.toString()asentrySet().toString().-
Methods inherited from class com.google.common.collect.ForwardingCollection
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, standardContainsAll, standardIsEmpty, standardToArray, standardToArray, toArray, toArray
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Methods inherited from class com.google.common.collect.ForwardingObject
toString
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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
addAll, clear, isEmpty, parallelStream, removeIf, stream, toArray, toArray, toArray
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Methods inherited from interface com.google.common.collect.Multiset
add, contains, containsAll, forEach, forEachEntry, iterator, remove, removeAll, retainAll, size, spliterator, toString
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Constructor Detail
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ForwardingMultiset
protected ForwardingMultiset()
Constructor for use by subclasses.
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Method Detail
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delegate
protected abstract Multiset<E> delegate()
Description copied from class:ForwardingObjectReturns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such asForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.- Specified by:
delegatein classForwardingCollection<E extends @Nullable Object>
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count
public int count(@CheckForNull Object element)
Description copied from interface:MultisetReturns 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:MultisetAdds 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:
addin interfaceMultiset<E extends @Nullable Object>- 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: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 ifoccurrences == 1, this is functionally equivalent to the callremove(element).- Specified by:
removein interfaceMultiset<E extends @Nullable Object>- 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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elementSet
public Set<E> elementSet()
Description copied from interface: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().- Specified by:
elementSetin 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:MultisetReturns a view of the contents of this multiset, grouped intoMultiset.Entryinstances, 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
Entryinstances 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 theEntryinstances 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 boolean equals(@CheckForNull Object object)
Description copied from class:java.lang.ObjectIndicates whether some other object is "equal to" this one.The
equalsmethod 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
xandy,x.equals(y)should returntrueif and only ify.equals(x)returnstrue. - It is transitive: for any non-null reference values
x,y, andz, ifx.equals(y)returnstrueandy.equals(z)returnstrue, thenx.equals(z)should returntrue. - It is consistent: for any non-null reference values
xandy, multiple invocations ofx.equals(y)consistently returntrueor consistently returnfalse, provided no information used inequalscomparisons on the objects is modified. - For any non-null reference value
x,x.equals(null)should returnfalse.
The
equalsmethod for classObjectimplements the most discriminating possible equivalence relation on objects; that is, for any non-null reference valuesxandy, this method returnstrueif and only ifxandyrefer to the same object (x == yhas the valuetrue).Note that it is generally necessary to override the
hashCodemethod whenever this method is overridden, so as to maintain the general contract for thehashCodemethod, which states that equal objects must have equal hash codes.- Specified by:
equalsin interfaceCollection<E extends @Nullable Object>- Specified by:
equalsin interfaceMultiset<E extends @Nullable Object>- Overrides:
equalsin classObject- Parameters:
object- the reference object with which to compare.- Returns:
trueif this object is the same as the obj argument;falseotherwise.- See Also:
Object.hashCode(),HashMap
- It is reflexive: for any non-null reference value
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hashCode
public int hashCode()
Description copied from class:java.lang.ObjectReturns 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
hashCodeis:- Whenever it is invoked on the same object more than once during
an execution of a Java application, the
hashCodemethod must consistently return the same integer, provided no information used inequalscomparisons 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 thehashCodemethod 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 thehashCodemethod 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
Objectdoes 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.)- Specified by:
hashCodein interfaceCollection<E extends @Nullable Object>- Specified by:
hashCodein interfaceMultiset<E extends @Nullable Object>- Overrides:
hashCodein 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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setCount
@CanIgnoreReturnValue public int setCount(E element, int count)
Description copied from interface:MultisetAdds or removes the necessary occurrences of an element such that the element attains the desired count.- Specified by:
setCountin interfaceMultiset<E extends @Nullable Object>- 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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setCount
@CanIgnoreReturnValue public boolean setCount(E element, int oldCount, int newCount)
Description copied from interface:MultisetConditionally 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:
setCountin 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:
trueif the condition for modification was met. This implies that the multiset was indeed modified, unlessoldCount == newCount.
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standardContains
protected boolean standardContains(@CheckForNull Object object)
A sensible definition ofForwardingCollection.contains(java.lang.Object)in terms ofcount(java.lang.Object). If you overridecount(java.lang.Object), you may wish to overrideForwardingCollection.contains(java.lang.Object)to forward to this implementation.- Overrides:
standardContainsin classForwardingCollection<E extends @Nullable Object>- Since:
- 7.0
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standardClear
protected void standardClear()
A sensible definition ofForwardingCollection.clear()in terms of theiteratormethod ofentrySet(). If you overrideentrySet(), you may wish to overrideForwardingCollection.clear()to forward to this implementation.- Overrides:
standardClearin classForwardingCollection<E extends @Nullable Object>- Since:
- 7.0
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standardCount
@Beta protected int standardCount(@CheckForNull Object object)
A sensible, albeit inefficient, definition ofcount(java.lang.Object)in terms ofentrySet(). If you overrideentrySet(), you may wish to overridecount(java.lang.Object)to forward to this implementation.- Since:
- 7.0
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standardAdd
protected boolean standardAdd(E element)
A sensible definition ofForwardingCollection.add(Object)in terms ofadd(Object, int). If you overrideadd(Object, int), you may wish to overrideForwardingCollection.add(Object)to forward to this implementation.- Since:
- 7.0
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standardAddAll
@Beta protected boolean standardAddAll(Collection<? extends E> elementsToAdd)
A sensible definition ofForwardingCollection.addAll(Collection)in terms ofForwardingCollection.add(Object)andadd(Object, int). If you override either of these methods, you may wish to overrideForwardingCollection.addAll(Collection)to forward to this implementation.- Overrides:
standardAddAllin classForwardingCollection<E extends @Nullable Object>- Since:
- 7.0
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standardRemove
protected boolean standardRemove(@CheckForNull Object element)
A sensible definition ofForwardingCollection.remove(Object)in terms ofremove(Object, int). If you overrideremove(Object, int), you may wish to overrideForwardingCollection.remove(Object)to forward to this implementation.- Overrides:
standardRemovein classForwardingCollection<E extends @Nullable Object>- Since:
- 7.0
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standardRemoveAll
protected boolean standardRemoveAll(Collection<?> elementsToRemove)
A sensible definition ofForwardingCollection.removeAll(java.util.Collection<?>)in terms of theremoveAllmethod ofelementSet(). If you overrideelementSet(), you may wish to overrideForwardingCollection.removeAll(java.util.Collection<?>)to forward to this implementation.- Overrides:
standardRemoveAllin classForwardingCollection<E extends @Nullable Object>- Since:
- 7.0
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standardRetainAll
protected boolean standardRetainAll(Collection<?> elementsToRetain)
A sensible definition ofForwardingCollection.retainAll(java.util.Collection<?>)in terms of theretainAllmethod ofelementSet(). If you overrideelementSet(), you may wish to overrideForwardingCollection.retainAll(java.util.Collection<?>)to forward to this implementation.- Overrides:
standardRetainAllin classForwardingCollection<E extends @Nullable Object>- Since:
- 7.0
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standardSetCount
protected int standardSetCount(E element, int count)
A sensible definition ofsetCount(Object, int)in terms ofcount(Object),add(Object, int), andremove(Object, int).entrySet(). If you override any of these methods, you may wish to overridesetCount(Object, int)to forward to this implementation.- Since:
- 7.0
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standardSetCount
protected boolean standardSetCount(E element, int oldCount, int newCount)
A sensible definition ofsetCount(Object, int, int)in terms ofcount(Object)andsetCount(Object, int). If you override either of these methods, you may wish to overridesetCount(Object, int, int)to forward to this implementation.- Since:
- 7.0
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standardIterator
protected Iterator<E> standardIterator()
A sensible definition ofForwardingCollection.iterator()in terms ofentrySet()andForwardingCollection.remove(Object). If you override either of these methods, you may wish to overrideForwardingCollection.iterator()to forward to this implementation.- Since:
- 7.0
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standardSize
protected int standardSize()
A sensible, albeit inefficient, definition ofForwardingCollection.size()in terms ofentrySet(). If you overrideentrySet(), you may wish to overrideForwardingCollection.size()to forward to this implementation.- Since:
- 7.0
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standardEquals
protected boolean standardEquals(@CheckForNull Object object)
A sensible, albeit inefficient, definition ofequals(java.lang.Object)in terms ofentrySet().size()andcount(java.lang.Object). If you override either of these methods, you may wish to overrideequals(java.lang.Object)to forward to this implementation.- Since:
- 7.0
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standardHashCode
protected int standardHashCode()
A sensible definition ofhashCode()asentrySet().hashCode(). If you overrideentrySet(), you may wish to overridehashCode()to forward to this implementation.- Since:
- 7.0
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standardToString
protected String standardToString()
A sensible definition ofForwardingObject.toString()asentrySet().toString(). If you overrideentrySet(), you may wish to overrideForwardingObject.toString()to forward to this implementation.- Overrides:
standardToStringin classForwardingCollection<E extends @Nullable Object>- Since:
- 7.0
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