--- a/jdk/src/java.base/share/classes/sun/misc/SoftCache.java Sun Apr 10 08:41:00 2016 -0700
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,462 +0,0 @@
-/*
- * Copyright (c) 1998, 2014, 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 sun.misc;
-
-import java.lang.ref.SoftReference;
-import java.lang.ref.ReferenceQueue;
-
-import java.util.Iterator;
-import java.util.Map;
-import java.util.AbstractMap;
-import java.util.HashMap;
-import java.util.Set;
-import java.util.AbstractSet;
-import java.util.NoSuchElementException;
-
-
-/**
- * A memory-sensitive implementation of the <code>Map</code> interface.
- *
- * <p> A <code>SoftCache</code> object uses {@link java.lang.ref.SoftReference
- * soft references} to implement a memory-sensitive hash map. If the garbage
- * collector determines at a certain point in time that a value object in a
- * <code>SoftCache</code> entry is no longer strongly reachable, then it may
- * remove that entry in order to release the memory occupied by the value
- * object. All <code>SoftCache</code> objects are guaranteed to be completely
- * cleared before the virtual machine will throw an
- * <code>OutOfMemoryError</code>. Because of this automatic clearing feature,
- * the behavior of this class is somewhat different from that of other
- * <code>Map</code> implementations.
- *
- * <p> Both null values and the null key are supported. This class has the
- * same performance characteristics as the <code>HashMap</code> class, and has
- * the same efficiency parameters of <em>initial capacity</em> and <em>load
- * factor</em>.
- *
- * <p> Like most collection classes, this class is not synchronized. A
- * synchronized <code>SoftCache</code> may be constructed using the
- * <code>Collections.synchronizedMap</code> method.
- *
- * <p> In typical usage this class will be subclassed and the <code>fill</code>
- * method will be overridden. When the <code>get</code> method is invoked on a
- * key for which there is no mapping in the cache, it will in turn invoke the
- * <code>fill</code> method on that key in an attempt to construct a
- * corresponding value. If the <code>fill</code> method returns such a value
- * then the cache will be updated and the new value will be returned. Thus,
- * for example, a simple URL-content cache can be constructed as follows:
- *
- * <pre>
- * public class URLCache extends SoftCache {
- * protected Object fill(Object key) {
- * return ((URL)key).getContent();
- * }
- * }
- * </pre>
- *
- * <p> The behavior of the <code>SoftCache</code> class depends in part upon
- * the actions of the garbage collector, so several familiar (though not
- * required) <code>Map</code> invariants do not hold for this class. <p>
- * Because entries are removed from a <code>SoftCache</code> in response to
- * dynamic advice from the garbage collector, a <code>SoftCache</code> may
- * behave as though an unknown thread is silently removing entries. In
- * particular, even if you synchronize on a <code>SoftCache</code> instance and
- * invoke none of its mutator methods, it is possible for the <code>size</code>
- * method to return smaller values over time, for the <code>isEmpty</code>
- * method to return <code>false</code> and then <code>true</code>, for the
- * <code>containsKey</code> method to return <code>true</code> and later
- * <code>false</code> for a given key, for the <code>get</code> method to
- * return a value for a given key but later return <code>null</code>, for the
- * <code>put</code> method to return <code>null</code> and the
- * <code>remove</code> method to return <code>false</code> for a key that
- * previously appeared to be in the map, and for successive examinations of the
- * key set, the value set, and the entry set to yield successively smaller
- * numbers of elements.
- *
- * @author Mark Reinhold
- * @since 1.2
- * @see java.util.HashMap
- * @see java.lang.ref.SoftReference
- * @deprecated No direct replacement; {@link java.util.WeakHashMap}
- * addresses a related by different use-case.
- */
-
-@Deprecated
-public class SoftCache extends AbstractMap<Object, Object> implements Map<Object, Object> {
-
- /* The basic idea of this implementation is to maintain an internal HashMap
- that maps keys to soft references whose referents are the keys' values;
- the various accessor methods dereference these soft references before
- returning values. Because we don't have access to the innards of the
- HashMap, each soft reference must contain the key that maps to it so
- that the processQueue method can remove keys whose values have been
- discarded. Thus the HashMap actually maps keys to instances of the
- ValueCell class, which is a simple extension of the SoftReference class.
- */
-
-
- private static class ValueCell extends SoftReference<Object> {
- private static Object INVALID_KEY = new Object();
- private static int dropped = 0;
- private Object key;
-
- private ValueCell(Object key, Object value, ReferenceQueue<Object> queue) {
- super(value, queue);
- this.key = key;
- }
-
- private static ValueCell create(Object key, Object value,
- ReferenceQueue<Object> queue)
- {
- if (value == null) return null;
- return new ValueCell(key, value, queue);
- }
-
- private static Object strip(Object val, boolean drop) {
- if (val == null) return null;
- ValueCell vc = (ValueCell)val;
- Object o = vc.get();
- if (drop) vc.drop();
- return o;
- }
-
- private boolean isValid() {
- return (key != INVALID_KEY);
- }
-
- private void drop() {
- super.clear();
- key = INVALID_KEY;
- dropped++;
- }
-
- }
-
-
- /* Hash table mapping keys to ValueCells */
- private Map<Object, Object> hash;
-
- /* Reference queue for cleared ValueCells */
- private ReferenceQueue<Object> queue = new ReferenceQueue<>();
-
-
- /* Process any ValueCells that have been cleared and enqueued by the
- garbage collector. This method should be invoked once by each public
- mutator in this class. We don't invoke this method in public accessors
- because that can lead to surprising ConcurrentModificationExceptions.
- */
- private void processQueue() {
- ValueCell vc;
- while ((vc = (ValueCell)queue.poll()) != null) {
- if (vc.isValid()) hash.remove(vc.key);
- else ValueCell.dropped--;
- }
- }
-
-
- /* -- Constructors -- */
-
- /**
- * Construct a new, empty <code>SoftCache</code> with the given
- * initial capacity and the given load factor.
- *
- * @param initialCapacity The initial capacity of the cache
- *
- * @param loadFactor A number between 0.0 and 1.0
- *
- * @throws IllegalArgumentException If the initial capacity is less than
- * or equal to zero, or if the load
- * factor is less than zero
- */
- public SoftCache(int initialCapacity, float loadFactor) {
- hash = new HashMap<>(initialCapacity, loadFactor);
- }
-
- /**
- * Construct a new, empty <code>SoftCache</code> with the given
- * initial capacity and the default load factor.
- *
- * @param initialCapacity The initial capacity of the cache
- *
- * @throws IllegalArgumentException If the initial capacity is less than
- * or equal to zero
- */
- public SoftCache(int initialCapacity) {
- hash = new HashMap<>(initialCapacity);
- }
-
- /**
- * Construct a new, empty <code>SoftCache</code> with the default
- * capacity and the default load factor.
- */
- public SoftCache() {
- hash = new HashMap<>();
- }
-
-
- /* -- Simple queries -- */
-
- /**
- * Return the number of key-value mappings in this cache. The time
- * required by this operation is linear in the size of the map.
- */
- public int size() {
- return entrySet().size();
- }
-
- /**
- * Return <code>true</code> if this cache contains no key-value mappings.
- */
- public boolean isEmpty() {
- return entrySet().isEmpty();
- }
-
- /**
- * Return <code>true</code> if this cache contains a mapping for the
- * specified key. If there is no mapping for the key, this method will not
- * attempt to construct one by invoking the <code>fill</code> method.
- *
- * @param key The key whose presence in the cache is to be tested
- */
- public boolean containsKey(Object key) {
- return ValueCell.strip(hash.get(key), false) != null;
- }
-
-
- /* -- Lookup and modification operations -- */
-
- /**
- * Create a value object for the given <code>key</code>. This method is
- * invoked by the <code>get</code> method when there is no entry for
- * <code>key</code>. If this method returns a non-<code>null</code> value,
- * then the cache will be updated to map <code>key</code> to that value,
- * and that value will be returned by the <code>get</code> method.
- *
- * <p> The default implementation of this method simply returns
- * <code>null</code> for every <code>key</code> value. A subclass may
- * override this method to provide more useful behavior.
- *
- * @param key The key for which a value is to be computed
- *
- * @return A value for <code>key</code>, or <code>null</code> if one
- * could not be computed
- * @see #get
- */
- protected Object fill(Object key) {
- return null;
- }
-
- /**
- * Return the value to which this cache maps the specified
- * <code>key</code>. If the cache does not presently contain a value for
- * this key, then invoke the <code>fill</code> method in an attempt to
- * compute such a value. If that method returns a non-<code>null</code>
- * value, then update the cache and return the new value. Otherwise,
- * return <code>null</code>.
- *
- * <p> Note that because this method may update the cache, it is considered
- * a mutator and may cause <code>ConcurrentModificationException</code>s to
- * be thrown if invoked while an iterator is in use.
- *
- * @param key The key whose associated value, if any, is to be returned
- *
- * @see #fill
- */
- public Object get(Object key) {
- processQueue();
- Object v = hash.get(key);
- if (v == null) {
- v = fill(key);
- if (v != null) {
- hash.put(key, ValueCell.create(key, v, queue));
- return v;
- }
- }
- return ValueCell.strip(v, false);
- }
-
- /**
- * Update this cache so that the given <code>key</code> maps to the given
- * <code>value</code>. If the cache previously contained a mapping for
- * <code>key</code> then that mapping is replaced and the old value is
- * returned.
- *
- * @param key The key that is to be mapped to the given
- * <code>value</code>
- * @param value The value to which the given <code>key</code> is to be
- * mapped
- *
- * @return The previous value to which this key was mapped, or
- * <code>null</code> if there was no mapping for the key
- */
- public Object put(Object key, Object value) {
- processQueue();
- ValueCell vc = ValueCell.create(key, value, queue);
- return ValueCell.strip(hash.put(key, vc), true);
- }
-
- /**
- * Remove the mapping for the given <code>key</code> from this cache, if
- * present.
- *
- * @param key The key whose mapping is to be removed
- *
- * @return The value to which this key was mapped, or <code>null</code> if
- * there was no mapping for the key
- */
- public Object remove(Object key) {
- processQueue();
- return ValueCell.strip(hash.remove(key), true);
- }
-
- /**
- * Remove all mappings from this cache.
- */
- public void clear() {
- processQueue();
- hash.clear();
- }
-
-
- /* -- Views -- */
-
- private static boolean valEquals(Object o1, Object o2) {
- return (o1 == null) ? (o2 == null) : o1.equals(o2);
- }
-
-
- /* Internal class for entries.
- Because it uses SoftCache.this.queue, this class cannot be static.
- */
- private class Entry implements Map.Entry<Object, Object> {
- private Map.Entry<Object, Object> ent;
- private Object value; /* Strong reference to value, to prevent the GC
- from flushing the value while this Entry
- exists */
-
- Entry(Map.Entry<Object, Object> ent, Object value) {
- this.ent = ent;
- this.value = value;
- }
-
- public Object getKey() {
- return ent.getKey();
- }
-
- public Object getValue() {
- return value;
- }
-
- public Object setValue(Object value) {
- return ent.setValue(ValueCell.create(ent.getKey(), value, queue));
- }
-
- @SuppressWarnings("unchecked")
- public boolean equals(Object o) {
- if (! (o instanceof Map.Entry)) return false;
- Map.Entry<Object, Object> e = (Map.Entry<Object, Object>)o;
- return (valEquals(ent.getKey(), e.getKey())
- && valEquals(value, e.getValue()));
- }
-
- public int hashCode() {
- Object k;
- return ((((k = getKey()) == null) ? 0 : k.hashCode())
- ^ ((value == null) ? 0 : value.hashCode()));
- }
-
- }
-
-
- /* Internal class for entry sets */
- private class EntrySet extends AbstractSet<Map.Entry<Object, Object>> {
- Set<Map.Entry<Object, Object>> hashEntries = hash.entrySet();
-
- public Iterator<Map.Entry<Object, Object>> iterator() {
-
- return new Iterator<Map.Entry<Object, Object>>() {
- Iterator<Map.Entry<Object, Object>> hashIterator = hashEntries.iterator();
- Entry next = null;
-
- public boolean hasNext() {
- while (hashIterator.hasNext()) {
- Map.Entry<Object, Object> ent = hashIterator.next();
- ValueCell vc = (ValueCell)ent.getValue();
- Object v = null;
- if ((vc != null) && ((v = vc.get()) == null)) {
- /* Value has been flushed by GC */
- continue;
- }
- next = new Entry(ent, v);
- return true;
- }
- return false;
- }
-
- public Map.Entry<Object, Object> next() {
- if ((next == null) && !hasNext())
- throw new NoSuchElementException();
- Entry e = next;
- next = null;
- return e;
- }
-
- public void remove() {
- hashIterator.remove();
- }
-
- };
- }
-
- public boolean isEmpty() {
- return !(iterator().hasNext());
- }
-
- public int size() {
- int j = 0;
- for (Iterator<Map.Entry<Object, Object>> i = iterator(); i.hasNext(); i.next()) j++;
- return j;
- }
-
- public boolean remove(Object o) {
- processQueue();
- if (o instanceof Entry) return hashEntries.remove(((Entry)o).ent);
- else return false;
- }
-
- }
-
-
- private Set<Map.Entry<Object, Object>> entrySet = null;
-
- /**
- * Return a <code>Set</code> view of the mappings in this cache.
- */
- public Set<Map.Entry<Object, Object>> entrySet() {
- if (entrySet == null) entrySet = new EntrySet();
- return entrySet;
- }
-
-}