|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object com.google.common.collect.ForwardingObject com.google.common.collect.ForwardingMap<K,V>
@GwtCompatible public abstract class ForwardingMap<K,V>
A map which forwards all its method calls to another map. Subclasses should override one or more methods to modify the behavior of the backing map as desired per the decorator pattern.
Warning: The methods of ForwardingMap
forward
indiscriminately to the methods of the delegate. For example,
overriding put(K, V)
alone will not change the behavior of putAll(java.util.Map extends K, ? extends V>)
, which can lead to unexpected behavior. In this case, you should
override putAll
as well, either providing your own implementation, or
delegating to the provided standardPutAll
method.
Each of the standard
methods, where appropriate, use Objects.equal(java.lang.Object, java.lang.Object)
to test equality for both keys and values. This may not be
the desired behavior for map implementations that use non-standard notions of
key equality, such as a SortedMap
whose comparator is not consistent
with equals
.
The standard
methods and the collection views they return are not
guaranteed to be thread-safe, even when all of the methods that they depend
on are thread-safe.
Nested Class Summary |
---|
Nested classes/interfaces inherited from interface java.util.Map |
---|
Map.Entry<K,V> |
Constructor Summary | |
---|---|
protected |
ForwardingMap()
Constructor for use by subclasses. |
Method Summary | |
---|---|
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. |
protected abstract Map<K,V> |
delegate()
Returns the backing delegate instance that methods are forwarded to. |
Set<Map.Entry<K,V>> |
entrySet()
Returns a Set view of the mappings contained in this map. |
boolean |
equals(Object object)
Indicates whether some other object is "equal to" this one. |
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. |
int |
hashCode()
Returns a hash code value for the object. |
boolean |
isEmpty()
Returns true if this map contains no key-value mappings. |
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). |
void |
putAll(Map<? extends K,? extends V> map)
Copies all of the mappings from the specified map to this map (optional operation). |
V |
remove(Object object)
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. |
protected void |
standardClear()
A sensible definition of clear() in terms of the iterator
method of entrySet() . |
protected boolean |
standardContainsKey(Object key)
A sensible, albeit inefficient, definition of containsKey(java.lang.Object) in terms
of the iterator method of entrySet() . |
protected boolean |
standardContainsValue(Object value)
A sensible definition of containsValue(java.lang.Object) in terms of the iterator method of entrySet() . |
protected Set<Map.Entry<K,V>> |
standardEntrySet(Supplier<Iterator<Map.Entry<K,V>>> entryIteratorSupplier)
A sensible definition of entrySet() in terms of the specified Supplier , which is used to generate iterators over the entry set, and in
terms of the following methods: clear() , containsKey(java.lang.Object) ,
get(java.lang.Object) , isEmpty() , remove(java.lang.Object) , and size() . |
protected boolean |
standardEquals(Object object)
A sensible definition of equals(java.lang.Object) in terms of the equals
method of entrySet() . |
protected int |
standardHashCode()
A sensible definition of hashCode() in terms of the iterator
method of entrySet() . |
protected boolean |
standardIsEmpty()
A sensible definition of isEmpty() in terms of the iterator
method of entrySet() . |
protected Set<K> |
standardKeySet()
A sensible definition of keySet() in terms of the following methods:
clear() , containsKey(java.lang.Object) , isEmpty() , remove(java.lang.Object) ,
size() , and the iterator method of entrySet() . |
protected void |
standardPutAll(Map<? extends K,? extends V> map)
A sensible definition of putAll(Map) in terms of put(Object, Object) . |
protected V |
standardRemove(Object key)
A sensible, albeit inefficient, definition of remove(java.lang.Object) in terms of
the iterator method of entrySet() . |
protected String |
standardToString()
A sensible definition of ForwardingObject.toString() in terms of the iterator
method of entrySet() . |
protected Collection<V> |
standardValues()
A sensible definition of values() in terms of the following methods:
clear() , containsValue(java.lang.Object) , isEmpty() , size() ,
and the iterator method of entrySet() . |
Collection<V> |
values()
Returns a Collection view of the values contained in this map. |
Methods inherited from class com.google.common.collect.ForwardingObject |
---|
toString |
Methods inherited from class java.lang.Object |
---|
clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
protected ForwardingMap()
Method Detail |
---|
protected abstract Map<K,V> delegate()
ForwardingObject
ForwardingSet.delegate()
. Concrete subclasses override this method to supply
the instance being decorated.
delegate
in class ForwardingObject
public int size()
java.util.Map
size
in interface Map<K,V>
public boolean isEmpty()
java.util.Map
isEmpty
in interface Map<K,V>
public V remove(Object object)
java.util.Map
(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.
remove
in interface Map<K,V>
object
- key whose mapping is to be removed from the map
public void clear()
java.util.Map
clear
in interface Map<K,V>
public boolean containsKey(Object key)
java.util.Map
containsKey
in interface Map<K,V>
key
- key whose presence in this map is to be tested
public boolean containsValue(Object value)
java.util.Map
containsValue
in interface Map<K,V>
value
- value whose presence in this map is to be tested
public V get(Object key)
java.util.Map
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.
get
in interface Map<K,V>
key
- the key whose associated value is to be returned
null
if this map contains no mapping for the keypublic V put(K key, V value)
java.util.Map
m.containsKey(k)
would return
true.)
put
in interface Map<K,V>
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified key
public void putAll(Map<? extends K,? extends V> map)
java.util.Map
put(k, v)
on this map once
for each mapping from key k to value v in the
specified map. The behavior of this operation is undefined if the
specified map is modified while the operation is in progress.
putAll
in interface Map<K,V>
map
- mappings to be stored in this mappublic Set<K> keySet()
java.util.Map
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.
keySet
in interface Map<K,V>
public Collection<V> values()
java.util.Map
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.
values
in interface Map<K,V>
public Set<Map.Entry<K,V>> entrySet()
java.util.Map
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.
entrySet
in interface Map<K,V>
public boolean equals(@Nullable Object object)
java.lang.Object
The equals
method implements an equivalence relation
on non-null object references:
x
, x.equals(x)
should return
true
.
x
and y
, x.equals(y)
should return true
if and only if
y.equals(x)
returns true
.
x
, y
, and z
, if
x.equals(y)
returns true
and
y.equals(z)
returns true
, then
x.equals(z)
should return true
.
x
and y
, multiple invocations of
x.equals(y) consistently return true
or consistently return false
, provided no
information used in equals
comparisons on the
objects is modified.
x
,
x.equals(null)
should return false
.
The equals method for class Object
implements
the most discriminating possible equivalence relation on objects;
that is, for any non-null reference values x
and
y
, this method returns true
if and only
if x
and y
refer to the same object
(x == y
has the value true
).
Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.
equals
in interface Map<K,V>
equals
in class Object
object
- the reference object with which to compare.
true
if this object is the same as the obj
argument; false
otherwise.Object.hashCode()
,
Hashtable
public int hashCode()
java.lang.Object
java.util.Hashtable
.
The general contract of hashCode
is:
hashCode
method on each of
the two objects must produce the same integer result.
Object.equals(java.lang.Object)
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 hashtables.
As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)
hashCode
in interface Map<K,V>
hashCode
in class Object
Object.equals(java.lang.Object)
,
Hashtable
@Beta protected void standardPutAll(Map<? extends K,? extends V> map)
putAll(Map)
in terms of put(Object, Object)
. If you override put(Object, Object)
, you
may wish to override putAll(Map)
to forward to this
implementation.
@Beta protected V standardRemove(@Nullable Object key)
remove(java.lang.Object)
in terms of
the iterator
method of entrySet()
. If you override entrySet()
, you may wish to override remove(java.lang.Object)
to forward to this
implementation.
Alternately, you may wish to override remove(java.lang.Object)
with keySet().remove
, assuming that approach would not lead to an infinite
loop.
@Beta protected void standardClear()
clear()
in terms of the iterator
method of entrySet()
. In many cases, you may wish to override
clear()
to forward to this implementation.
@Beta protected Set<K> standardKeySet()
keySet()
in terms of the following methods:
clear()
, containsKey(java.lang.Object)
, isEmpty()
, remove(java.lang.Object)
,
size()
, and the iterator
method of entrySet()
. In
many cases, you may wish to override keySet()
to forward to this
implementation.
@Beta protected boolean standardContainsKey(@Nullable Object key)
containsKey(java.lang.Object)
in terms
of the iterator
method of entrySet()
. If you override entrySet()
, you may wish to override containsKey(java.lang.Object)
to forward to
this implementation.
@Beta protected Collection<V> standardValues()
values()
in terms of the following methods:
clear()
, containsValue(java.lang.Object)
, isEmpty()
, size()
,
and the iterator
method of entrySet()
. In many cases, you
may wish to override values()
to forward to this implementation.
@Beta protected boolean standardContainsValue(@Nullable Object value)
containsValue(java.lang.Object)
in terms of the iterator
method of entrySet()
. If you override entrySet()
,
you may wish to override containsValue(java.lang.Object)
to forward to this
implementation.
@Beta protected Set<Map.Entry<K,V>> standardEntrySet(Supplier<Iterator<Map.Entry<K,V>>> entryIteratorSupplier)
entrySet()
in terms of the specified Supplier
, which is used to generate iterators over the entry set, and in
terms of the following methods: clear()
, containsKey(java.lang.Object)
,
get(java.lang.Object)
, isEmpty()
, remove(java.lang.Object)
, and size()
. In many
cases, you may wish to override entrySet()
to forward to this
implementation.
entryIteratorSupplier
- A creator for iterators over the entry set.
Each call to get
must return an iterator that will
traverse the entire entry set.@Beta protected boolean standardIsEmpty()
isEmpty()
in terms of the iterator
method of entrySet()
. If you override entrySet()
, you may
wish to override isEmpty()
to forward to this implementation.
@Beta protected boolean standardEquals(@Nullable Object object)
equals(java.lang.Object)
in terms of the equals
method of entrySet()
. If you override entrySet()
, you may
wish to override equals(java.lang.Object)
to forward to this implementation.
@Beta protected int standardHashCode()
hashCode()
in terms of the iterator
method of entrySet()
. If you override entrySet()
, you may
wish to override hashCode()
to forward to this implementation.
@Beta protected String standardToString()
ForwardingObject.toString()
in terms of the iterator
method of entrySet()
. If you override entrySet()
, you may
wish to override ForwardingObject.toString()
to forward to this implementation.
|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |