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PhantomReference
public
class
PhantomReference
extends Reference<T>
Phantom reference objects, which are enqueued after the collector
determines that their referents may otherwise be reclaimed. Phantom
references are most often used to schedule post-mortem cleanup actions.
Suppose the garbage collector determines at a certain point in time
that an object is
phantom reachable. At that time it will atomically clear
all phantom references to that object and all phantom references to
any other phantom-reachable objects from which that object is reachable.
At the same time or at some later time it will enqueue those newly-cleared
phantom references that are registered with reference queues.
In order to ensure that a reclaimable object remains so, the referent of
a phantom reference may not be retrieved: The get
method of a
phantom reference always returns null
.
Summary
Public constructors |
PhantomReference(T referent, ReferenceQueue<? super T> q)
Creates a new phantom reference that refers to the given object and
is registered with the given queue.
|
Public methods |
T
|
get()
Returns this reference object's referent.
|
Inherited methods |
From class
java.lang.ref.Reference
void
|
clear()
Clears this reference object.
|
Object
|
clone()
Throws CloneNotSupportedException .
|
boolean
|
enqueue()
Adds this reference object to the queue with which it is registered,
if any.
|
T
|
get()
Returns this reference object's referent.
|
boolean
|
isEnqueued()
This method was deprecated
in API level 31.
This method was never implemented to test if a reference object has
been cleared and enqueued as it was previously specified since 1.2.
This method could be misused due to the inherent race condition
or without an associated ReferenceQueue .
An application relying on this method to release critical resources
could cause serious performance issue.
An application should use ReferenceQueue to reliably determine
what reference objects that have been enqueued or
refersTo(null) to determine if this reference
object has been cleared.
|
static
void
|
reachabilityFence(Object ref)
Ensures that the object referenced by the given reference remains
strongly reachable,
regardless of any prior actions of the program that might otherwise cause
the object to become unreachable; thus, the referenced object is not
reclaimable by garbage collection at least until after the invocation of
this method.
|
final
boolean
|
refersTo(T obj)
Tests if the referent of this reference object is obj .
|
|
From class
java.lang.Object
Object
|
clone()
Creates and returns a copy of this object.
|
boolean
|
equals(Object obj)
Indicates whether some other object is "equal to" this one.
|
void
|
finalize()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
|
final
Class<?>
|
getClass()
Returns the runtime class of this Object .
|
int
|
hashCode()
Returns a hash code value for the object.
|
final
void
|
notify()
Wakes up a single thread that is waiting on this object's
monitor.
|
final
void
|
notifyAll()
Wakes up all threads that are waiting on this object's monitor.
|
String
|
toString()
Returns a string representation of the object.
|
final
void
|
wait(long timeoutMillis, int nanos)
Causes the current thread to wait until it is awakened, typically
by being notified or interrupted, or until a
certain amount of real time has elapsed.
|
final
void
|
wait(long timeoutMillis)
Causes the current thread to wait until it is awakened, typically
by being notified or interrupted, or until a
certain amount of real time has elapsed.
|
final
void
|
wait()
Causes the current thread to wait until it is awakened, typically
by being notified or interrupted.
|
|
Public constructors
PhantomReference
public PhantomReference (T referent,
ReferenceQueue<? super T> q)
Creates a new phantom reference that refers to the given object and
is registered with the given queue.
It is possible to create a phantom reference with a null
queue, but such a reference is completely useless: Its get
method will always return null
and, since it does not have a queue,
it will never be enqueued.
Parameters |
referent |
T : the object the new phantom reference will refer to |
q |
ReferenceQueue : the queue with which the reference is to be registered,
or null if registration is not required |
Public methods
get
public T get ()
Returns this reference object's referent. Because the referent of a
phantom reference is always inaccessible, this method always returns
null
.
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Last updated 2025-02-10 UTC.
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