com.google.common.collect

Class HashBiMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

com.google.common.collect.HashBiMap<K,V>

All Implemented Interfaces:

BiMap<K,V>, Serializable, Map<K,V>

@GwtCompatible(emulated=true)
public final class HashBiMap<K,V>
extends AbstractMap<K,V>
implements BiMap<K,V>, Serializable

A BiMap backed by two hash tables. This implementation allows null keys and values. A HashBiMap and its inverse are both serializable.

See the Guava User Guide article on BiMap .

Since:

2.0 (imported from Google Collections Library)

Author:

Louis Wasserman, Mike Bostock

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Removes all of the mappings from this map (optional operation).
boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
static <K,V> HashBiMap<K,V>	create() Returns a new, empty HashBiMap with the default initial capacity (16).
static <K,V> HashBiMap<K,V>	create(int expectedSize) Constructs a new, empty bimap with the specified expected size.
static <K,V> HashBiMap<K,V>	create(Map<? extends K,? extends V> map) Constructs a new bimap containing initial values from map.
Set<Map.Entry<K,V>>	entrySet() Returns a Set view of the mappings contained in this map.
V	forcePut(K key, V value) An alternate form of put that silently removes any existing entry with the value value before proceeding with the BiMap.put(K, V) operation.
V	get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
BiMap<V,K>	inverse() Returns the inverse view of this bimap, which maps each of this bimap's values to its associated key.
Set<K>	keySet() Returns a Set view of the keys contained in this map.
V	put(K key, V value) Associates the specified value with the specified key in this map (optional operation).
V	remove(Object key) Removes the mapping for a key from this map if it is present (optional operation).
int	size() Returns the number of key-value mappings in this map.
Set<V>	values() Returns a Collection view of the values contained in this map.

Methods inherited from class java.util.AbstractMap

clone, equals, hashCode, isEmpty, putAll, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.google.common.collect.BiMap

putAll

Methods inherited from interface java.util.Map

equals, hashCode, isEmpty

Method Detail

create

public static <K,V> HashBiMap<K,V> create()

Returns a new, empty HashBiMap with the default initial capacity (16).

create

public static <K,V> HashBiMap<K,V> create(int expectedSize)

Constructs a new, empty bimap with the specified expected size.

Parameters:

expectedSize - the expected number of entries

Throws:

IllegalArgumentException - if the specified expected size is negative

create

public static <K,V> HashBiMap<K,V> create(Map<? extends K,? extends V> map)

Constructs a new bimap containing initial values from map. The bimap is created with an initial capacity sufficient to hold the mappings in the specified map.

containsKey

public boolean containsKey(@Nullable
                  Object key)

Description copied from class: java.util.AbstractMap

Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.)

This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractMap<K,V>

Parameters:

key - key whose presence in this map is to be tested

Returns:

true if this map contains a mapping for the specified key

containsValue

public boolean containsValue(@Nullable
                    Object value)

Description copied from class: java.util.AbstractMap

Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations of the Map interface.

This implementation iterates over entrySet() searching for an entry with the specified value. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map.

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractMap<K,V>

Parameters:

value - value whose presence in this map is to be tested

Returns:

true if this map maps one or more keys to the specified value

get

@Nullable
public V get(@Nullable
             Object key)

Description copied from class: java.util.AbstractMap

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

More formally, if this map contains a mapping from a key k to a value v such that (key==null ? k==null : key.equals(k)), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

If this map permits null values, then a return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, the entry's value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

Parameters:

key - the key whose associated value is to be returned

Returns:

the value to which the specified key is mapped, or null if this map contains no mapping for the key

put

public V put(@Nullable
    K key,
    @Nullable
    V value)

Description copied from class: java.util.AbstractMap

Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)

This implementation always throws an UnsupportedOperationException.

Specified by:

put in interface BiMap<K,V>

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractMap<K,V>

Parameters:

key - key with which the specified value is to be associated

value - value to be associated with the specified key

Returns:

the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key, if the implementation supports null values.)

forcePut

public V forcePut(@Nullable
         K key,
         @Nullable
         V value)

Description copied from interface: BiMap

An alternate form of put that silently removes any existing entry with the value value before proceeding with the BiMap.put(K, V) operation. If the bimap previously contained the provided key-value mapping, this method has no effect.

Note that a successful call to this method could cause the size of the bimap to increase by one, stay the same, or even decrease by one.

Warning: If an existing entry with this value is removed, the key for that entry is discarded and not returned.

Specified by:

forcePut in interface BiMap<K,V>

Parameters:

key - the key with which the specified value is to be associated

value - the value to be associated with the specified key

Returns:

the value which was previously associated with the key, which may be null, or null if there was no previous entry

remove

public V remove(@Nullable
       Object key)

Description copied from class: java.util.AbstractMap

Removes the mapping for a key from this map if it is present (optional operation). More formally, if this map contains a mapping from key k to value v such that (key==null ? k==null : key.equals(k)), that mapping is removed. (The map can contain at most one such mapping.)

Returns the value to which this map previously associated the key, or null if the map contained no mapping for the key.

If this map permits null values, then a return value of null does not necessarily indicate that the map contained no mapping for the key; it's also possible that the map explicitly mapped the key to null.

The map will not contain a mapping for the specified key once the call returns.

This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, its value is obtained with its getValue operation, the entry is removed from the collection (and the backing map) with the iterator's remove operation, and the saved value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

Note that this implementation throws an UnsupportedOperationException if the entrySet iterator does not support the remove method and this map contains a mapping for the specified key.

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMap<K,V>

Parameters:

key - key whose mapping is to be removed from the map

Returns:

the previous value associated with key, or null if there was no mapping for key.

clear

public void clear()

Description copied from class: java.util.AbstractMap

Removes all of the mappings from this map (optional operation). The map will be empty after this call returns.

This implementation calls entrySet().clear().

Note that this implementation throws an UnsupportedOperationException if the entrySet does not support the clear operation.

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class AbstractMap<K,V>

size

public int size()

Description copied from class: java.util.AbstractMap

Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

This implementation returns entrySet().size().

Specified by:

size in interface Map<K,V>

Overrides:

size in class AbstractMap<K,V>

Returns:

the number of key-value mappings in this map

keySet

public Set<K> keySet()

Description copied from class: java.util.AbstractMap

Returns a Set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

This implementation returns a set that subclasses AbstractSet. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsKey method.

The set is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same set.

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractMap<K,V>

Returns:

a set view of the keys contained in this map

values

public Set<V> values()

Description copied from class: java.util.AbstractMap

Returns a Collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

This implementation returns a collection that subclasses AbstractCollection. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsValue method.

The collection is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same collection.

Specified by:

values in interface BiMap<K,V>

Specified by:

values in interface Map<K,V>

Overrides:

values in class AbstractMap<K,V>

Returns:

a collection view of the values contained in this map

entrySet

public Set<Map.Entry<K,V>> entrySet()

Description copied from interface: java.util.Map

Returns a Set view of the mappings contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation, or through the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in class AbstractMap<K,V>

Returns:

a set view of the mappings contained in this map

inverse

public BiMap<V,K> inverse()

Description copied from interface: BiMap

Returns the inverse view of this bimap, which maps each of this bimap's values to its associated key. The two bimaps are backed by the same data; any changes to one will appear in the other.

Note:There is no guaranteed correspondence between the iteration order of a bimap and that of its inverse.

Specified by:

inverse in interface BiMap<K,V>

Returns:

the inverse view of this bimap