Class ForwardingObject
- Direct Known Subclasses:
ForwardingCache
,ForwardingCollection
,ForwardingExecutorService
,ForwardingFuture
,ForwardingIterator
,ForwardingMap
,ForwardingMapEntry
,ForwardingMultimap
,ForwardingTable
delegate()
method must be overridden to return the instance
being decorated.
This class does not forward the hashCode
and equals
methods through to the backing object, but relies on Object
's
implementation. This is necessary to preserve the symmetry of equals
.
Custom definitions of equality are usually based on an interface, such as
Set
or List
, so that the implementation of equals
can
cast the object being tested for equality to the custom interface.
ForwardingObject
implements no such custom interfaces directly; they
are implemented only in subclasses. Therefore, forwarding equals
would break symmetry, as the forwarding object might consider itself equal to
the object being tested, but the reverse could not be true. This behavior is
consistent with the JDK's collection wrappers, such as
Collections.unmodifiableCollection(java.util.Collection<? extends T>)
. Use an
interface-specific subclass of ForwardingObject
, such as ForwardingList
, to preserve equality behavior, or override equals
directly.
The toString
method is forwarded to the delegate. Although this
class does not implement Serializable
, a serializable subclass may be
created since this class has a parameter-less constructor.
- Since:
- 2.0
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Constructor Summary
Constructors -
Method Summary
-
Constructor Details
-
ForwardingObject
protected ForwardingObject()Constructor for use by subclasses.
-
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Method Details
-
delegate
Returns 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. -
toString
Returns the string representation generated by the delegate'stoString
method.
-