2362N/A * Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved. 0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 0N/A * This code is free software; you can redistribute it and/or modify it 0N/A * under the terms of the GNU General Public License version 2 only, as 2362N/A * published by the Free Software Foundation. Oracle designates this 0N/A * particular file as subject to the "Classpath" exception as provided 2362N/A * by Oracle in the LICENSE file that accompanied this code. 0N/A * This code is distributed in the hope that it will be useful, but WITHOUT 0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 0N/A * version 2 for more details (a copy is included in the LICENSE file that 0N/A * accompanied this code). 0N/A * You should have received a copy of the GNU General Public License version 0N/A * 2 along with this work; if not, write to the Free Software Foundation, 0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 2362N/A * or visit www.oracle.com if you need additional information or have any 0N/A * Soft reference objects, which are cleared at the discretion of the garbage 0N/A * collector in response to memory demand. Soft references are most often used 0N/A * to implement memory-sensitive caches. 0N/A * <p> Suppose that the garbage collector determines at a certain point in time 0N/A * reachable</a>. At that time it may choose to clear atomically all soft 0N/A * references to that object and all soft references to any other 0N/A * softly-reachable objects from which that object is reachable through a chain 0N/A * of strong references. At the same time or at some later time it will 0N/A * enqueue those newly-cleared soft references that are registered with 0N/A * <p> All soft references to softly-reachable objects are guaranteed to have 0N/A * been cleared before the virtual machine throws an 0N/A * <code>OutOfMemoryError</code>. Otherwise no constraints are placed upon the 0N/A * time at which a soft reference will be cleared or the order in which a set 0N/A * of such references to different objects will be cleared. Virtual machine 0N/A * implementations are, however, encouraged to bias against clearing 0N/A * recently-created or recently-used soft references. 0N/A * <p> Direct instances of this class may be used to implement simple caches; 0N/A * this class or derived subclasses may also be used in larger data structures 0N/A * to implement more sophisticated caches. As long as the referent of a soft 0N/A * reference is strongly reachable, that is, is actually in use, the soft 0N/A * reference will not be cleared. Thus a sophisticated cache can, for example, 0N/A * prevent its most recently used entries from being discarded by keeping 0N/A * strong referents to those entries, leaving the remaining entries to be 0N/A * discarded at the discretion of the garbage collector. 0N/A * @author Mark Reinhold 1036N/A * Timestamp clock, updated by the garbage collector 1036N/A * Timestamp updated by each invocation of the get method. The VM may use 0N/A * this field when selecting soft references to be cleared, but it is not 0N/A * required to do so. 0N/A * Creates a new soft reference that refers to the given object. The new 0N/A * reference is not registered with any queue. 0N/A * @param referent object the new soft reference will refer to 0N/A * Creates a new soft reference that refers to the given object and is 0N/A * registered with the given queue. 0N/A * @param referent object the new soft reference will refer to 0N/A * @param q the queue with which the reference is to be registered, 0N/A * or <tt>null</tt> if registration is not required 0N/A * Returns this reference object's referent. If this reference object has 0N/A * been cleared, either by the program or by the garbage collector, then 0N/A * this method returns <code>null</code>. 0N/A * @return The object to which this reference refers, or 0N/A * <code>null</code> if this reference object has been cleared