@GwtCompatible public abstract class ForwardingMapEntry<K,V> extends ForwardingObject implements Map.Entry<K,V>
Warning: The methods of ForwardingMapEntry
forward indiscriminately to
the methods of the delegate. For example, overriding getValue()
alone will not
change the behavior of equals(java.lang.Object)
, which can lead to unexpected behavior. In this case, you
should override equals
as well, either providing your own implementation, or delegating
to the provided standardEquals
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 the entry of a SortedMap
whose
comparator is not consistent with equals
.
The standard
methods are not guaranteed to be thread-safe, even when all of the
methods that they depend on are thread-safe.
Modifier | Constructor and Description |
---|---|
protected |
ForwardingMapEntry()
Constructor for use by subclasses.
|
Modifier and Type | Method and Description |
---|---|
protected abstract Map.Entry<K,V> |
delegate()
Returns the backing delegate instance that methods are forwarded to.
|
boolean |
equals(@Nullable Object object)
Indicates whether some other object is "equal to" this one.
|
K |
getKey()
Returns the key corresponding to this entry.
|
V |
getValue()
Returns the value corresponding to this entry.
|
int |
hashCode()
Returns a hash code value for the object.
|
V |
setValue(V value)
Replaces the value corresponding to this entry with the specified
value (optional operation).
|
protected boolean |
standardEquals(@Nullable Object object)
|
protected int |
standardHashCode()
|
protected String |
standardToString()
|
toString
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
comparingByKey, comparingByKey, comparingByValue, comparingByValue
protected ForwardingMapEntry()
protected abstract Map.Entry<K,V> delegate()
ForwardingObject
ForwardingSet.delegate()
. Concrete subclasses override this method to supply the
instance being decorated.delegate
in class ForwardingObject
public K getKey()
java.util.Map.Entry
public V getValue()
java.util.Map.Entry
public V setValue(V value)
java.util.Map.Entry
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.
public int hashCode()
java.lang.Object
HashMap
.
The general contract of hashCode
is:
hashCode
method
must consistently return the same integer, provided no information
used in equals
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.
equals(Object)
method, then calling the 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 hash tables.
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
Java™ programming language.)
hashCode
in interface Map.Entry<K,V>
hashCode
in class Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
protected boolean standardEquals(@Nullable Object object)
equals(Object)
in terms of getKey()
and getValue()
. If you override either of these methods, you may wish to override equals(Object)
to forward to this implementation.protected int standardHashCode()
hashCode()
in terms of getKey()
and getValue()
. If you override either of these methods, you may wish to override hashCode()
to forward to this implementation.@Beta protected String standardToString()
ForwardingObject.toString()
in terms of getKey()
and getValue()
.
If you override either of these methods, you may wish to override equals(java.lang.Object)
to forward to
this implementation.Copyright © 2010–2018. All rights reserved.