@CheckReturnValue @ParametersAreNonnullByDefault

Package com.google.common.collect

Collection interfaces and implementations, and other utilities for collections. This package is a part of the open-source Guava library.

The classes in this package include:

Immutable collections

These are collections whose contents will never change. They also offer a few additional guarantees (see ImmutableCollection for details). Implementations are available for both the JDK collection types and the Guava collection types (listed below).

Collection types

Multimap

A new type, which is similar to Map, but may contain multiple entries with the same key. Some behaviors of Multimap are left unspecified and are provided only by the subtypes mentioned below.

ListMultimap

An extension of Multimap which permits duplicate entries, supports random access of values for a particular key, and has partially order-dependent equality as defined by ListMultimap.equals(Object). ListMultimap takes its name from the fact that the collection of values associated with a given key fulfills the List contract.

SetMultimap

An extension of Multimap which has order-independent equality and does not allow duplicate entries; that is, while a key may appear twice in a SetMultimap, each must map to a different value. SetMultimap takes its name from the fact that the collection of values associated with a given key fulfills the Set contract.

SortedSetMultimap

An extension of SetMultimap for which the collection values associated with a given key is a SortedSet.

BiMap

An extension of Map that guarantees the uniqueness of its values as well as that of its keys. This is sometimes called an "invertible map," since the restriction on values enables it to support an inverse view -- which is another instance of BiMap.

Table

A new type, which is similar to Map, but which indexes its values by an ordered pair of keys, a row key and column key.

Multiset

An extension of Collection that may contain duplicate values like a List, yet has order-independent equality like a Set. One typical use for a multiset is to represent a histogram.

ClassToInstanceMap

An extension of Map that associates a raw type with an instance of that type.

Ranges

• Range
• RangeMap
• RangeSet
• DiscreteDomain
• ContiguousSet

Classes of static utility methods

• Collections2
• Comparators
• Iterables
• Iterators
• Lists
• Maps
• MoreCollectors
• Multimaps
• Multisets
• ObjectArrays
• Queues
• Sets
• Streams
• Tables

Abstract implementations

• AbstractIterator
• AbstractSequentialIterator
• UnmodifiableIterator
• UnmodifiableListIterator

Forwarding collections

We provide implementations of collections that forward all method calls to a delegate collection by default. Subclasses can override one or more methods to implement the decorator pattern. For an example, see ForwardingCollection.

Other

• EvictingQueue
• Interner, Interners
• MapMaker
• MinMaxPriorityQueue
• PeekingIterator

Interface Summary

Interface	Description
BiMap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A bimap (or "bidirectional map") is a map that preserves the uniqueness of its values as well as that of its keys.
ClassToInstanceMap<B extends @Nullable java.lang.Object>	A map, each entry of which maps a Java raw type to an instance of that type.
Interner<E>	Provides similar behavior to String.intern() for any immutable type.
ListMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A Multimap that can hold duplicate key-value pairs and that maintains the insertion ordering of values for a given key.
MapDifference<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	An object representing the differences between two maps.
MapDifference.ValueDifference<V extends @Nullable java.lang.Object>	A difference between the mappings from two maps with the same key.
Maps.EntryTransformer<K extends @Nullable java.lang.Object,V1 extends @Nullable java.lang.Object,V2 extends @Nullable java.lang.Object>	A transformation of the value of a key-value pair, using both key and value as inputs.
Multimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A collection that maps keys to values, similar to Map, but in which each key may be associated with multiple values.
Multiset<E extends @Nullable java.lang.Object>	A collection that supports order-independent equality, like Set, but may have duplicate elements.
Multiset.Entry<E extends @Nullable java.lang.Object>	An unmodifiable element-count pair for a multiset.
PeekingIterator<E extends @Nullable java.lang.Object>	An iterator that supports a one-element lookahead while iterating.
RangeMap<K extends java.lang.Comparable,V>	A mapping from disjoint nonempty ranges to non-null values.
RangeSet<C extends java.lang.Comparable>	A set comprising zero or more nonempty, disconnected ranges of type C.
RowSortedTable<R extends @Nullable java.lang.Object,C extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	Interface that extends Table and whose rows are sorted.
SetMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A Multimap that cannot hold duplicate key-value pairs.
SortedMapDifference<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	An object representing the differences between two sorted maps.
SortedMultiset<E extends @Nullable java.lang.Object>	A Multiset which maintains the ordering of its elements, according to either their natural order or an explicit Comparator.
SortedSetMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A SetMultimap whose set of values for a given key are kept sorted; that is, they comprise a SortedSet.
Table<R extends @Nullable java.lang.Object,C extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A collection that associates an ordered pair of keys, called a row key and a column key, with a single value.
Table.Cell<R extends @Nullable java.lang.Object,C extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	Row key / column key / value triplet corresponding to a mapping in a table.

Class Summary

Class	Description
AbstractIterator<T extends @Nullable java.lang.Object>	This class provides a skeletal implementation of the Iterator interface, to make this interface easier to implement for certain types of data sources.
AbstractSequentialIterator<T>	This class provides a skeletal implementation of the Iterator interface for sequences whose next element can always be derived from the previous element.
ArrayListMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	Implementation of Multimap that uses an ArrayList to store the values for a given key.
ArrayTable<R,C,V>	Fixed-size Table implementation backed by a two-dimensional array.
Collections2	Provides static methods for working with Collection instances.
Comparators	Provides static methods for working with Comparator instances.
ComparisonChain	A utility for performing a chained comparison statement.
ConcurrentHashMultiset<E>	A multiset that supports concurrent modifications and that provides atomic versions of most Multiset operations (exceptions where noted).
ContiguousSet<C extends java.lang.Comparable>	A sorted set of contiguous values in a given DiscreteDomain.
DiscreteDomain<C extends java.lang.Comparable>	A descriptor for a discrete Comparable domain such as all Integer instances.
EnumBiMap<K extends java.lang.Enum<K>,V extends java.lang.Enum<V>>	A BiMap backed by two EnumMap instances.
EnumHashBiMap<K extends java.lang.Enum<K>,V extends @Nullable java.lang.Object>	A BiMap backed by an EnumMap instance for keys-to-values, and a HashMap instance for values-to-keys.
EnumMultiset<E extends java.lang.Enum<E>>	Multiset implementation specialized for enum elements, supporting all single-element operations in O(1).
EvictingQueue<E>	A non-blocking queue which automatically evicts elements from the head of the queue when attempting to add new elements onto the queue and it is full.
FluentIterable<E extends @Nullable java.lang.Object>	An expanded Iterable API, providing functionality similar to Java 8's powerful streams library in a slightly different way.
ForwardingBlockingDeque<E>	Deprecated. This class has moved to com.google.common.util.concurrent.
ForwardingCollection<E extends @Nullable java.lang.Object>	A collection which forwards all its method calls to another collection.
ForwardingConcurrentMap<K,V>	A concurrent map which forwards all its method calls to another concurrent map.
ForwardingDeque<E extends @Nullable java.lang.Object>	A deque which forwards all its method calls to another deque.
ForwardingIterator<T extends @Nullable java.lang.Object>	An iterator which forwards all its method calls to another iterator.
ForwardingList<E extends @Nullable java.lang.Object>	A list which forwards all its method calls to another list.
ForwardingListIterator<E extends @Nullable java.lang.Object>	A list iterator which forwards all its method calls to another list iterator.
ForwardingListMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A list multimap which forwards all its method calls to another list multimap.
ForwardingMap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A map which forwards all its method calls to another map.
ForwardingMapEntry<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A map entry which forwards all its method calls to another map entry.
ForwardingMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A multimap which forwards all its method calls to another multimap.
ForwardingMultiset<E extends @Nullable java.lang.Object>	A multiset which forwards all its method calls to another multiset.
ForwardingNavigableMap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A navigable map which forwards all its method calls to another navigable map.
ForwardingNavigableSet<E extends @Nullable java.lang.Object>	A navigable set which forwards all its method calls to another navigable set.
ForwardingObject	An abstract base class for implementing the decorator pattern.
ForwardingQueue<E extends @Nullable java.lang.Object>	A queue which forwards all its method calls to another queue.
ForwardingSet<E extends @Nullable java.lang.Object>	A set which forwards all its method calls to another set.
ForwardingSetMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A set multimap which forwards all its method calls to another set multimap.
ForwardingSortedMap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A sorted map which forwards all its method calls to another sorted map.
ForwardingSortedMultiset<E extends @Nullable java.lang.Object>	A sorted multiset which forwards all its method calls to another sorted multiset.
ForwardingSortedSet<E extends @Nullable java.lang.Object>	A sorted set which forwards all its method calls to another sorted set.
ForwardingSortedSetMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A sorted set multimap which forwards all its method calls to another sorted set multimap.
ForwardingTable<R extends @Nullable java.lang.Object,C extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A table which forwards all its method calls to another table.
HashBasedTable<R,C,V>	Implementation of Table using linked hash tables.
HashBiMap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	A BiMap backed by two hash tables.
HashMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	Implementation of Multimap using hash tables.
HashMultiset<E extends @Nullable java.lang.Object>	Multiset implementation that uses hashing for key and entry access.
ImmutableBiMap<K,V>	A BiMap whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableBiMap.Builder<K,V>	A builder for creating immutable bimap instances, especially public static final bimaps ("constant bimaps").
ImmutableClassToInstanceMap<B>	A ClassToInstanceMap whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableClassToInstanceMap.Builder<B>	A builder for creating immutable class-to-instance maps.
ImmutableCollection<E>	A Collection whose contents will never change, and which offers a few additional guarantees detailed below.
ImmutableCollection.Builder<E>	Abstract base class for builders of ImmutableCollection types.
ImmutableList<E>	A List whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableList.Builder<E>	A builder for creating immutable list instances, especially public static final lists ("constant lists").
ImmutableListMultimap<K,V>	A ListMultimap whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableListMultimap.Builder<K,V>	A builder for creating immutable ListMultimap instances, especially public static final multimaps ("constant multimaps").
ImmutableMap<K,V>	A Map whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableMap.Builder<K,V>	A builder for creating immutable map instances, especially public static final maps ("constant maps").
ImmutableMultimap<K,V>	A Multimap whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableMultimap.Builder<K,V>	A builder for creating immutable multimap instances, especially public static final multimaps ("constant multimaps").
ImmutableMultiset<E>	A Multiset whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableMultiset.Builder<E>	A builder for creating immutable multiset instances, especially public static final multisets ("constant multisets").
ImmutableRangeMap<K extends java.lang.Comparable<?>,V>	A RangeMap whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableRangeMap.Builder<K extends java.lang.Comparable<?>,V>	A builder for immutable range maps.
ImmutableRangeSet<C extends java.lang.Comparable>	A RangeSet whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableRangeSet.Builder<C extends java.lang.Comparable<?>>	A builder for immutable range sets.
ImmutableSet<E>	A Set whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableSet.Builder<E>	A builder for creating ImmutableSet instances.
ImmutableSetMultimap<K,V>	A SetMultimap whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableSetMultimap.Builder<K,V>	A builder for creating immutable SetMultimap instances, especially public static final multimaps ("constant multimaps").
ImmutableSortedMap<K,V>	A NavigableMap whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableSortedMap.Builder<K,V>	A builder for creating immutable sorted map instances, especially public static final maps ("constant maps").
ImmutableSortedMultiset<E>	A SortedMultiset whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableSortedMultiset.Builder<E>	A builder for creating immutable multiset instances, especially public static final multisets ("constant multisets").
ImmutableSortedSet<E>	A NavigableSet whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableSortedSet.Builder<E>	A builder for creating immutable sorted set instances, especially public static final sets ("constant sets"), with a given comparator.
ImmutableTable<R,C,V>	A Table whose contents will never change, with many other important properties detailed at ImmutableCollection.
ImmutableTable.Builder<R,C,V>	A builder for creating immutable table instances, especially public static final tables ("constant tables").
Interners	Contains static methods pertaining to instances of Interner.
Interners.InternerBuilder	Builder for Interner instances.
Iterables	An assortment of mainly legacy static utility methods that operate on or return objects of type Iterable.
Iterators	This class contains static utility methods that operate on or return objects of type Iterator.
LinkedHashMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	Implementation of Multimap that does not allow duplicate key-value entries and that returns collections whose iterators follow the ordering in which the data was added to the multimap.
LinkedHashMultiset<E extends @Nullable java.lang.Object>	A Multiset implementation with predictable iteration order.
LinkedListMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	An implementation of ListMultimap that supports deterministic iteration order for both keys and values.
Lists	Static utility methods pertaining to List instances.
MapMaker	A builder of ConcurrentMap instances that can have keys or values automatically wrapped in weak references.
Maps	Static utility methods pertaining to Map instances (including instances of SortedMap, BiMap, etc.).
MinMaxPriorityQueue<E>	A double-ended priority queue, which provides constant-time access to both its least element and its greatest element, as determined by the queue's specified comparator.
MinMaxPriorityQueue.Builder<B>	The builder class used in creation of min-max priority queues.
MoreCollectors	Collectors not present in java.util.stream.Collectors that are not otherwise associated with a com.google.common type.
MultimapBuilder<K0 extends @Nullable java.lang.Object,V0 extends @Nullable java.lang.Object>	An immutable builder for Multimap instances, letting you independently select the desired behaviors (for example, ordering) of the backing map and value-collections.
MultimapBuilder.ListMultimapBuilder<K0 extends @Nullable java.lang.Object,V0 extends @Nullable java.lang.Object>	A specialization of MultimapBuilder that generates ListMultimap instances.
MultimapBuilder.MultimapBuilderWithKeys<K0 extends @Nullable java.lang.Object>	An intermediate stage in a MultimapBuilder in which the key-value collection map implementation has been specified, but the value collection implementation has not.
MultimapBuilder.SetMultimapBuilder<K0 extends @Nullable java.lang.Object,V0 extends @Nullable java.lang.Object>	A specialization of MultimapBuilder that generates SetMultimap instances.
MultimapBuilder.SortedSetMultimapBuilder<K0 extends @Nullable java.lang.Object,V0 extends @Nullable java.lang.Object>	A specialization of MultimapBuilder that generates SortedSetMultimap instances.
Multimaps	Provides static methods acting on or generating a Multimap.
Multisets	Provides static utility methods for creating and working with Multiset instances.
MutableClassToInstanceMap<B extends @Nullable java.lang.Object>	A mutable class-to-instance map backed by an arbitrary user-provided map.
ObjectArrays	Static utility methods pertaining to object arrays.
Ordering<T extends @Nullable java.lang.Object>	A comparator, with additional methods to support common operations.
Queues	Static utility methods pertaining to Queue and Deque instances.
Range<C extends java.lang.Comparable>	A range (or "interval") defines the boundaries around a contiguous span of values of some Comparable type; for example, "integers from 1 to 100 inclusive." Note that it is not possible to iterate over these contained values.
Sets	Static utility methods pertaining to Set instances.
Sets.SetView<E extends @Nullable java.lang.Object>	An unmodifiable view of a set which may be backed by other sets; this view will change as the backing sets do.
Tables	Provides static methods that involve a Table.
TreeBasedTable<R,C,V>	Implementation of Table whose row keys and column keys are ordered by their natural ordering or by supplied comparators.
TreeMultimap<K extends @Nullable java.lang.Object,V extends @Nullable java.lang.Object>	Implementation of Multimap whose keys and values are ordered by their natural ordering or by supplied comparators.
TreeMultiset<E extends @Nullable java.lang.Object>	A multiset which maintains the ordering of its elements, according to either their natural order or an explicit Comparator.
TreeRangeMap<K extends java.lang.Comparable,V>	An implementation of RangeMap based on a TreeMap, supporting all optional operations.
TreeRangeSet<C extends java.lang.Comparable<?>>	An implementation of RangeSet backed by a TreeMap.
TreeTraverser<T>	Deprecated. Use Traverser instead.
UnmodifiableIterator<E extends @Nullable java.lang.Object>	An iterator that does not support UnmodifiableIterator.remove().
UnmodifiableListIterator<E extends @Nullable java.lang.Object>	A list iterator that does not support UnmodifiableIterator.remove(), UnmodifiableListIterator.add(E), or UnmodifiableListIterator.set(E).

Enum Summary

Enum	Description
BoundType	Indicates whether an endpoint of some range is contained in the range itself ("closed") or not ("open").

Exception Summary

Exception	Description
ComputationException	Deprecated. This exception is no longer thrown by com.google.common.