diff -r 000000000000 -r 5198affdb915 emul/compact/src/main/java/java/lang/ref/SoftReference.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/emul/compact/src/main/java/java/lang/ref/SoftReference.java Mon Jan 28 18:12:47 2013 +0100 @@ -0,0 +1,118 @@ +/* + * Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. Oracle designates this + * particular file as subject to the "Classpath" exception as provided + * by Oracle in the LICENSE file that accompanied this code. + * + * This code 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 + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + */ + +package java.lang.ref; + + +/** + * Soft reference objects, which are cleared at the discretion of the garbage + * collector in response to memory demand. Soft references are most often used + * to implement memory-sensitive caches. + * + *
Suppose that the garbage collector determines at a certain point in time + * that an object is softly + * reachable. At that time it may choose to clear atomically all soft + * references to that object and all soft references to any other + * softly-reachable objects from which that object is reachable through a chain + * of strong references. At the same time or at some later time it will + * enqueue those newly-cleared soft references that are registered with + * reference queues. + * + *
All soft references to softly-reachable objects are guaranteed to have
+ * been cleared before the virtual machine throws an
+ * OutOfMemoryError
. Otherwise no constraints are placed upon the
+ * time at which a soft reference will be cleared or the order in which a set
+ * of such references to different objects will be cleared. Virtual machine
+ * implementations are, however, encouraged to bias against clearing
+ * recently-created or recently-used soft references.
+ *
+ *
Direct instances of this class may be used to implement simple caches;
+ * this class or derived subclasses may also be used in larger data structures
+ * to implement more sophisticated caches. As long as the referent of a soft
+ * reference is strongly reachable, that is, is actually in use, the soft
+ * reference will not be cleared. Thus a sophisticated cache can, for example,
+ * prevent its most recently used entries from being discarded by keeping
+ * strong referents to those entries, leaving the remaining entries to be
+ * discarded at the discretion of the garbage collector.
+ *
+ * @author Mark Reinhold
+ * @since 1.2
+ */
+
+public class SoftReferencenull
.
+ *
+ * @return The object to which this reference refers, or
+ * null
if this reference object has been cleared
+ */
+ public T get() {
+ T o = super.get();
+ if (o != null && this.timestamp != clock)
+ this.timestamp = clock;
+ return o;
+ }
+
+}