java.lang.ref
Class Reference<T>
This is the base class of all references. A reference allows
refering to an object without preventing the garbage collector to
collect it. The only way to get the referred object is via the
get()-method. This method will return
null if the object was collected.
A reference may be registered with a queue. When a referred
element gets collected the reference will be put on the queue, so
that you will be notified.
There are currently three types of references: soft reference,
weak reference and phantom reference.
Soft references will be cleared if the garbage collector is told
to free some memory and there are no unreferenced or weakly referenced
objects. It is useful for caches.
Weak references will be cleared as soon as the garbage collector
determines that the refered object is only weakly reachable. They
are useful as keys in hashtables (see WeakHashtable) as
you get notified when nobody has the key anymore.
Phantom references don't prevent finalization. If an object is only
phantom reachable, it will be finalized, and the reference will be
enqueued, but not cleared. Since you mustn't access an finalized
object, the get method of a phantom reference will never
work. It is useful to keep track, when an object is finalized.
void | clear()- Clears the reference, so that it doesn't refer to its object
anymore.
|
boolean | enqueue()- Enqueue an object on a reference queue.
|
T | get()- Returns the object, this reference refers to.
|
boolean | isEnqueued()- Tells if the object is enqueued on a reference queue.
|
clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait |
clear
public void clear()
Clears the reference, so that it doesn't refer to its object
anymore. For soft and weak references this is called by the
garbage collector. For phantom references you should call
this when enqueuing the reference.
enqueue
public boolean enqueue()
Enqueue an object on a reference queue. This is normally executed
by the garbage collector.
get
public T get()
Returns the object, this reference refers to.
- the object, this reference refers to, or null if the
reference was cleared.
isEnqueued
public boolean isEnqueued()
Tells if the object is enqueued on a reference queue.
- true if it is enqueued, false otherwise.
java.lang.ref.Reference
Copyright (C) 1999, 2002, 2003, 2004, 2006 Free Software Foundation, Inc.
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module. An independent module is a module which is not derived from
or based on this library. If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so. If you do not wish to do so, delete this
exception statement from your version.