/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.rx_cache2.internal.cache.memory.apache;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* An abstract implementation of a hash-based map that allows the entries to
* be removed by the garbage collector.
* <p>
* This class implements all the features necessary for a subclass reference
* hash-based map. Key-value entries are stored in instances of the
* <code>ReferenceEntry</code> class which can be overridden and replaced.
* The iterators can similarly be replaced, without the need to replace the KeySet,
* EntrySet and Values view classes.
* <p>
* Overridable methods are provided to change the default hashing behaviour, and
* to change how entries are added to and removed from the map. Hopefully, all you
* need for unusual subclasses is here.
* <p>
* When you construct an <code>AbstractReferenceMap</code>, you can specify what
* kind of references are used to store the map's keys and values.
* If non-hard references are used, then the garbage collector can remove
* mappings if a key or value becomes unreachable, or if the JVM's memory is
* running low. For information on how the different reference types behave,
* see {@link Reference}.
* <p>
* Different types of references can be specified for keys and values.
* The keys can be configured to be weak but the values hard,
* in which case this class will behave like a
* <a href="http://java.sun.com/j2se/1.4/docs/api/java/util/WeakHashMap.html">
* <code>WeakHashMap</code></a>. However, you can also specify hard keys and
* weak values, or any other combination. The default constructor uses
* hard keys and soft values, providing a memory-sensitive cache.
* <p>
* This {@link Map} implementation does <i>not</i> allow null elements.
* Attempting to addOrUpdate a null key or value to the map will raise a
* <code>NullPointerException</code>.
* <p>
* All the available iterators can be reset back to the start by casting to
* <code>ResettableIterator</code> and calling <code>reset()</code>.
* <p>
* This implementation is not synchronized.
* You can use {@link java.util.Collections#synchronizedMap} to
* provide synchronized access to a <code>ReferenceMap</code>.
*
* @see java.lang.ref.Reference
* @since 3.1 (extracted from ReferenceMap in 3.0)
* @version $Id: AbstractReferenceMap.java 1477799 2013-04-30 19:56:11Z tn $
*/
public abstract class AbstractReferenceMap<K, V> extends
io.rx_cache2.internal.cache.memory.apache.AbstractHashedMap<K, V> {
/**
* Reference type enum.
*/
public static enum ReferenceStrength {
HARD(0), SOFT(1), WEAK(2);
/** value */
public final int value;
/**
* Resolve enum from int.
* @param value the int value
* @return ReferenceType
* @throws IllegalArgumentException if the specified value is invalid.
*/
public static ReferenceStrength resolve(final int value) {
switch (value) {
case 0:
return HARD;
case 1:
return SOFT;
case 2:
return WEAK;
default:
throw new IllegalArgumentException();
}
}
private ReferenceStrength(final int value) {
this.value = value;
}
}
/**
* The reference type for keys.
*/
private ReferenceStrength keyType;
/**
* The reference type for values.
*/
private ReferenceStrength valueType;
/**
* Should the value be automatically purged when the associated key has been collected?
*/
private boolean purgeValues;
/**
* ReferenceQueue used to eliminate stale mappings.
* See purge.
*/
private transient ReferenceQueue<Object> queue;
//-----------------------------------------------------------------------
/**
* Constructor used during deserialization.
*/
protected AbstractReferenceMap() {
super();
}
/**
* Constructs a new empty map with the specified reference types,
* load factor and initial capacity.
*
* @param keyType the type of reference to use for keys;
* must be {@link ReferenceStrength#HARD HARD},
* {@link ReferenceStrength#SOFT SOFT},
* {@link ReferenceStrength#WEAK WEAK}
* @param valueType the type of reference to use for values;
* must be {@link ReferenceStrength#HARD},
* {@link ReferenceStrength#SOFT SOFT},
* {@link ReferenceStrength#WEAK WEAK}
* @param capacity the initial capacity for the map
* @param loadFactor the load factor for the map
* @param purgeValues should the value be automatically purged when the
* key is garbage collected
*/
protected AbstractReferenceMap(
final ReferenceStrength keyType, final ReferenceStrength valueType, final int capacity,
final float loadFactor, final boolean purgeValues) {
super(capacity, loadFactor);
this.keyType = keyType;
this.valueType = valueType;
this.purgeValues = purgeValues;
}
/**
* Initialise this subclass during construction, cloning or deserialization.
*/
@Override
protected void init() {
queue = new ReferenceQueue<Object>();
}
//-----------------------------------------------------------------------
/**
* Gets the size of the map.
*
* @return the size
*/
@Override
public int size() {
purgeBeforeRead();
return super.size();
}
/**
* Checks whether the map is currently empty.
*
* @return true if the map is currently size zero
*/
@Override
public boolean isEmpty() {
purgeBeforeRead();
return super.isEmpty();
}
/**
* Checks whether the map contains the specified key.
*
* @param key the key to search for
* @return true if the map contains the key
*/
@Override
public boolean containsKey(final Object key) {
purgeBeforeRead();
final Entry<K, V> entry = getEntry(key);
if (entry == null) {
return false;
}
return entry.getValue() != null;
}
/**
* Checks whether the map contains the specified value.
*
* @param value the value to search for
* @return true if the map contains the value
*/
@Override
public boolean containsValue(final Object value) {
purgeBeforeRead();
if (value == null) {
return false;
}
return super.containsValue(value);
}
/**
* Gets the value mapped to the key specified.
*
* @param key the key
* @return the mapped value, null if no match
*/
@Override
public V get(final Object key) {
purgeBeforeRead();
final Entry<K, V> entry = getEntry(key);
if (entry == null) {
return null;
}
return entry.getValue();
}
/**
* Puts a key-value mapping into this map.
* Neither the key nor the value may be null.
*
* @param key the key to addOrUpdate, must not be null
* @param value the value to addOrUpdate, must not be null
* @return the value previously mapped to this key, null if none
* @throws NullPointerException if either the key or value is null
*/
@Override
public V put(final K key, final V value) {
if (key == null) {
throw new NullPointerException("null keys not allowed");
}
if (value == null) {
throw new NullPointerException("null values not allowed");
}
purgeBeforeWrite();
return super.put(key, value);
}
/**
* Removes the specified mapping from this map.
*
* @param key the mapping to remove
* @return the value mapped to the removed key, null if key not in map
*/
@Override
public V remove(final Object key) {
if (key == null) {
return null;
}
purgeBeforeWrite();
return super.remove(key);
}
/**
* Clears this map.
*/
@Override
public void clear() {
super.clear();
while (queue.poll() != null) {} // drain the queue
}
//-----------------------------------------------------------------------
/**
* Gets a MapIterator over the reference map.
* The iterator only returns valid key/value pairs.
*
* @return a map iterator
*/
@Override
public io.rx_cache2.internal.cache.memory.apache.MapIterator<K, V> mapIterator() {
return new ReferenceMapIterator<K, V>(this);
}
/**
* Returns a set view of this map's entries.
* An iterator returned entry is valid until <code>next()</code> is called again.
* The <code>setValue()</code> method on the <code>toArray</code> entries has no effect.
*
* @return a set view of this map's entries
*/
@Override
public Set<Map.Entry<K, V>> entrySet() {
if (entrySet == null) {
entrySet = new ReferenceEntrySet<K, V>(this);
}
return entrySet;
}
/**
* Returns a set view of this map's keys.
*
* @return a set view of this map's keys
*/
@Override
public Set<K> keySet() {
if (keySet == null) {
keySet = new ReferenceKeySet<K>(this);
}
return keySet;
}
/**
* Returns a collection view of this map's values.
*
* @return a set view of this map's values
*/
@Override
public Collection<V> values() {
if (values == null) {
values = new ReferenceValues<V>(this);
}
return values;
}
//-----------------------------------------------------------------------
/**
* Purges stale mappings from this map before read operations.
* <p>
* This implementation calls {@link #purge()} to maintain a consistent state.
*/
protected void purgeBeforeRead() {
purge();
}
/**
* Purges stale mappings from this map before write operations.
* <p>
* This implementation calls {@link #purge()} to maintain a consistent state.
*/
protected void purgeBeforeWrite() {
purge();
}
/**
* Purges stale mappings from this map.
* <p>
* Note that this method is not synchronized! Special
* care must be taken if, for instance, you want stale
* mappings to be removed on a periodic basis by some
* background thread.
*/
protected void purge() {
Reference<?> ref = queue.poll();
while (ref != null) {
purge(ref);
ref = queue.poll();
}
}
/**
* Purges the specified reference.
*
* @param ref the reference to purge
*/
protected void purge(final Reference<?> ref) {
// The hashCode of the reference is the hashCode of the
// mapping key, even if the reference refers to the
// mapping value...
final int hash = ref.hashCode();
final int index = hashIndex(hash, data.length);
HashEntry<K, V> previous = null;
HashEntry<K, V> entry = data[index];
while (entry != null) {
if (((ReferenceEntry<K, V>) entry).purge(ref)) {
if (previous == null) {
data[index] = entry.next;
} else {
previous.next = entry.next;
}
this.size--;
return;
}
previous = entry;
entry = entry.next;
}
}
//-----------------------------------------------------------------------
/**
* Gets the entry mapped to the key specified.
*
* @param key the key
* @return the entry, null if no match
*/
@Override
protected HashEntry<K, V> getEntry(final Object key) {
if (key == null) {
return null;
}
return super.getEntry(key);
}
/**
* Gets the hash code for a MapEntry.
* Subclasses can override this, for example to use the identityHashCode.
*
* @param key the key to get a hash code for, may be null
* @param value the value to get a hash code for, may be null
* @return the hash code, as per the MapEntry specification
*/
protected int hashEntry(final Object key, final Object value) {
return (key == null ? 0 : key.hashCode()) ^
(value == null ? 0 : value.hashCode());
}
/**
* Compares two keys, in internal converted form, to see if they are equal.
* <p>
* This implementation converts the key from the entry to a real reference
* before comparison.
*
* @param key1 the first key to compare passed in from outside
* @param key2 the second key extracted from the entry via <code>entry.key</code>
* @return true if equal
*/
@Override
@SuppressWarnings("unchecked")
protected boolean isEqualKey(final Object key1, Object key2) {
key2 = keyType == ReferenceStrength.HARD ? key2 : ((Reference<K>) key2).get();
return key1 == key2 || key1.equals(key2);
}
/**
* Creates a ReferenceEntry instead of a HashEntry.
*
* @param next the next entry in sequence
* @param hashCode the hash code to use
* @param key the key to store
* @param value the value to store
* @return the newly created entry
*/
@Override
protected ReferenceEntry<K, V> createEntry(final HashEntry<K, V> next, final int hashCode,
final K key, final V value) {
return new ReferenceEntry<K, V>(this, next, hashCode, key, value);
}
/**
* Creates an entry set iterator.
*
* @return the entrySet iterator
*/
@Override
protected Iterator<Map.Entry<K, V>> createEntrySetIterator() {
return new ReferenceEntrySetIterator<K, V>(this);
}
/**
* Creates an key set iterator.
*
* @return the keySet iterator
*/
@Override
protected Iterator<K> createKeySetIterator() {
return new ReferenceKeySetIterator<K>(this);
}
/**
* Creates an values iterator.
*
* @return the values iterator
*/
@Override
protected Iterator<V> createValuesIterator() {
return new ReferenceValuesIterator<V>(this);
}
//-----------------------------------------------------------------------
/**
* EntrySet implementation.
*/
static class ReferenceEntrySet<K, V> extends EntrySet<K, V> {
protected ReferenceEntrySet(final io.rx_cache2.internal.cache.memory.apache.AbstractHashedMap<K, V> parent) {
super(parent);
}
@Override
public Object[] toArray() {
return toArray(new Object[size()]);
}
@Override
public <T> T[] toArray(final T[] arr) {
// special implementation to handle disappearing entries
final ArrayList<Map.Entry<K, V>> list = new ArrayList<Map.Entry<K, V>>(size());
for (final Map.Entry<K, V> entry : this) {
list.add(new DefaultMapEntry<K, V>(entry));
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* KeySet implementation.
*/
static class ReferenceKeySet<K> extends KeySet<K> {
protected ReferenceKeySet(final io.rx_cache2.internal.cache.memory.apache.AbstractHashedMap<K, ?> parent) {
super(parent);
}
@Override
public Object[] toArray() {
return toArray(new Object[size()]);
}
@Override
public <T> T[] toArray(final T[] arr) {
// special implementation to handle disappearing keys
final List<K> list = new ArrayList<K>(size());
for (final K key : this) {
list.add(key);
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* Values implementation.
*/
static class ReferenceValues<V> extends Values<V> {
protected ReferenceValues(final io.rx_cache2.internal.cache.memory.apache.AbstractHashedMap<?, V> parent) {
super(parent);
}
@Override
public Object[] toArray() {
return toArray(new Object[size()]);
}
@Override
public <T> T[] toArray(final T[] arr) {
// special implementation to handle disappearing values
final List<V> list = new ArrayList<V>(size());
for (final V value : this) {
list.add(value);
}
return list.toArray(arr);
}
}
//-----------------------------------------------------------------------
/**
* A MapEntry implementation for the map.
* <p>
* If getKey() or getValue() returns null, it means
* the mapping is stale and should be removed.
*
* @since 3.1
*/
protected static class ReferenceEntry<K, V> extends HashEntry<K, V> {
/** The parent map */
private final AbstractReferenceMap<K, V> parent;
/**
* Creates a new entry object for the ReferenceMap.
*
* @param parent the parent map
* @param next the next entry in the hash bucket
* @param hashCode the hash code of the key
* @param key the key
* @param value the value
*/
public ReferenceEntry(final AbstractReferenceMap<K, V> parent, final HashEntry<K, V> next,
final int hashCode, final K key, final V value) {
super(next, hashCode, null, null);
this.parent = parent;
this.key = toReference(parent.keyType, key, hashCode);
this.value = toReference(parent.valueType, value, hashCode); // the key hashCode is passed in deliberately
}
/**
* Gets the key from the entry.
* This method dereferences weak and soft keys and thus may return null.
*
* @return the key, which may be null if it was garbage collected
*/
@Override
@SuppressWarnings("unchecked")
public K getKey() {
return (K) (parent.keyType == ReferenceStrength.HARD ? key : ((Reference<K>) key).get());
}
/**
* Gets the value from the entry.
* This method dereferences weak and soft value and thus may return null.
*
* @return the value, which may be null if it was garbage collected
*/
@Override
@SuppressWarnings("unchecked")
public V getValue() {
return (V) (parent.valueType == ReferenceStrength.HARD ? value : ((Reference<V>) value).get());
}
/**
* Sets the value of the entry.
*
* @param obj the object to store
* @return the previous value
*/
@Override
@SuppressWarnings("unchecked")
public V setValue(final V obj) {
final V old = getValue();
if (parent.valueType != ReferenceStrength.HARD) {
((Reference<V>) value).clear();
}
value = toReference(parent.valueType, obj, hashCode);
return old;
}
/**
* Compares this map entry to another.
* <p>
* This implementation uses <code>isEqualKey</code> and
* <code>isEqualValue</code> on the main map for comparison.
*
* @param obj the other map entry to compare to
* @return true if equal, false if not
*/
@Override
public boolean equals(final Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Map.Entry == false) {
return false;
}
final Map.Entry<?, ?> entry = (Map.Entry<?, ?>)obj;
final Object entryKey = entry.getKey(); // convert to hard reference
final Object entryValue = entry.getValue(); // convert to hard reference
if (entryKey == null || entryValue == null) {
return false;
}
// compare using map methods, aiding identity subclass
// note that key is direct access and value is via method
return parent.isEqualKey(entryKey, key) &&
parent.isEqualValue(entryValue, getValue());
}
/**
* Gets the hashcode of the entry using temporary hard references.
* <p>
* This implementation uses <code>hashEntry</code> on the main map.
*
* @return the hashcode of the entry
*/
@Override
public int hashCode() {
return parent.hashEntry(getKey(), getValue());
}
/**
* Constructs a reference of the given type to the given referent.
* The reference is registered with the queue for later purging.
*
* @param <T> the type of the referenced object
* @param type HARD, SOFT or WEAK
* @param referent the object to refer to
* @param hash the hash code of the <i>key</i> of the mapping;
* this number might be different from referent.hashCode() if
* the referent represents a value and not a key
* @return the reference to the object
*/
protected <T> Object toReference(final ReferenceStrength type, final T referent, final int hash) {
if (type == ReferenceStrength.HARD) {
return referent;
}
if (type == ReferenceStrength.SOFT) {
return new SoftRef<T>(hash, referent, parent.queue);
}
if (type == ReferenceStrength.WEAK) {
return new WeakRef<T>(hash, referent, parent.queue);
}
throw new Error();
}
/**
* Purges the specified reference
* @param ref the reference to purge
* @return true or false
*/
boolean purge(final Reference<?> ref) {
boolean r = parent.keyType != ReferenceStrength.HARD && key == ref;
r = r || parent.valueType != ReferenceStrength.HARD && value == ref;
if (r) {
if (parent.keyType != ReferenceStrength.HARD) {
((Reference<?>) key).clear();
}
if (parent.valueType != ReferenceStrength.HARD) {
((Reference<?>) value).clear();
} else if (parent.purgeValues) {
value = null;
}
}
return r;
}
/**
* Gets the next entry in the bucket.
*
* @return the next entry in the bucket
*/
protected ReferenceEntry<K, V> next() {
return (ReferenceEntry<K, V>) next;
}
}
//-----------------------------------------------------------------------
/**
* Base iterator class.
*/
static class ReferenceBaseIterator<K, V> {
/** The parent map */
final AbstractReferenceMap<K, V> parent;
// These fields keep track of where we are in the table.
int index;
ReferenceEntry<K, V> entry;
ReferenceEntry<K, V> previous;
// These Object fields provide hard references to the
// current and next entry; this assures that if hasNext()
// returns true, next() will actually return a valid element.
K currentKey, nextKey;
V currentValue, nextValue;
int expectedModCount;
public ReferenceBaseIterator(final AbstractReferenceMap<K, V> parent) {
super();
this.parent = parent;
index = parent.size() != 0 ? parent.data.length : 0;
// have to do this here! size() invocation above
// may have altered the modCount.
expectedModCount = parent.modCount;
}
public boolean hasNext() {
checkMod();
while (nextNull()) {
ReferenceEntry<K, V> e = entry;
int i = index;
while (e == null && i > 0) {
i--;
e = (ReferenceEntry<K, V>) parent.data[i];
}
entry = e;
index = i;
if (e == null) {
currentKey = null;
currentValue = null;
return false;
}
nextKey = e.getKey();
nextValue = e.getValue();
if (nextNull()) {
entry = entry.next();
}
}
return true;
}
private void checkMod() {
if (parent.modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
private boolean nextNull() {
return nextKey == null || nextValue == null;
}
protected ReferenceEntry<K, V> nextEntry() {
checkMod();
if (nextNull() && !hasNext()) {
throw new NoSuchElementException();
}
previous = entry;
entry = entry.next();
currentKey = nextKey;
currentValue = nextValue;
nextKey = null;
nextValue = null;
return previous;
}
protected ReferenceEntry<K, V> currentEntry() {
checkMod();
return previous;
}
public void remove() {
checkMod();
if (previous == null) {
throw new IllegalStateException();
}
parent.remove(currentKey);
previous = null;
currentKey = null;
currentValue = null;
expectedModCount = parent.modCount;
}
}
/**
* The EntrySet iterator.
*/
static class ReferenceEntrySetIterator<K, V>
extends ReferenceBaseIterator<K, V> implements Iterator<Map.Entry<K, V>> {
public ReferenceEntrySetIterator(final AbstractReferenceMap<K, V> parent) {
super(parent);
}
public Map.Entry<K, V> next() {
return nextEntry();
}
}
/**
* The keySet iterator.
*/
static class ReferenceKeySetIterator<K> extends ReferenceBaseIterator<K, Object> implements Iterator<K> {
@SuppressWarnings("unchecked")
ReferenceKeySetIterator(final AbstractReferenceMap<K, ?> parent) {
super((AbstractReferenceMap<K, Object>) parent);
}
public K next() {
return nextEntry().getKey();
}
}
/**
* The values iterator.
*/
static class ReferenceValuesIterator<V> extends ReferenceBaseIterator<Object, V> implements Iterator<V> {
@SuppressWarnings("unchecked")
ReferenceValuesIterator(final AbstractReferenceMap<?, V> parent) {
super((AbstractReferenceMap<Object, V>) parent);
}
public V next() {
return nextEntry().getValue();
}
}
/**
* The MapIterator implementation.
*/
static class ReferenceMapIterator<K, V> extends ReferenceBaseIterator<K, V> implements
io.rx_cache2.internal.cache.memory.apache.MapIterator<K, V> {
protected ReferenceMapIterator(final AbstractReferenceMap<K, V> parent) {
super(parent);
}
public K next() {
return nextEntry().getKey();
}
public K getKey() {
final HashEntry<K, V> current = currentEntry();
if (current == null) {
throw new IllegalStateException(GETKEY_INVALID);
}
return current.getKey();
}
public V getValue() {
final HashEntry<K, V> current = currentEntry();
if (current == null) {
throw new IllegalStateException(GETVALUE_INVALID);
}
return current.getValue();
}
public V setValue(final V value) {
final HashEntry<K, V> current = currentEntry();
if (current == null) {
throw new IllegalStateException(SETVALUE_INVALID);
}
return current.setValue(value);
}
}
//-----------------------------------------------------------------------
// These two classes store the hashCode of the key of
// of the mapping, so that after they're dequeued a quick
// lookup of the bucket in the table can occur.
/**
* A soft reference holder.
*/
static class SoftRef<T> extends SoftReference<T> {
/** the hashCode of the key (even if the reference points to a value) */
private final int hash;
public SoftRef(final int hash, final T r, final ReferenceQueue<? super T> q) {
super(r, q);
this.hash = hash;
}
@Override
public int hashCode() {
return hash;
}
}
/**
* A weak reference holder.
*/
static class WeakRef<T> extends WeakReference<T> {
/** the hashCode of the key (even if the reference points to a value) */
private final int hash;
public WeakRef(final int hash, final T r, final ReferenceQueue<? super T> q) {
super(r, q);
this.hash = hash;
}
@Override
public int hashCode() {
return hash;
}
}
//-----------------------------------------------------------------------
/**
* Replaces the superclass method to store the state of this class.
* <p>
* Serialization is not one of the JDK's nicest topics. Normal serialization will
* initialise the superclass before the subclass. Sometimes however, this isn't
* what you want, as in this case the <code>put()</code> method on read can be
* affected by subclass state.
* <p>
* The solution adopted here is to serialize the state data of this class in
* this protected method. This method must be called by the
* <code>writeObject()</code> of the first serializable subclass.
* <p>
* Subclasses may override if they have a specific field that must be present
* on read before this implementation will work. Generally, the read determines
* what must be serialized here, if anything.
*
* @param out the output stream
* @throws IOException if an error occurs while writing to the stream
*/
@Override
protected void doWriteObject(final ObjectOutputStream out) throws IOException {
out.writeInt(keyType.value);
out.writeInt(valueType.value);
out.writeBoolean(purgeValues);
out.writeFloat(loadFactor);
out.writeInt(data.length);
for (final io.rx_cache2.internal.cache.memory.apache.MapIterator<K, V> it = mapIterator(); it.hasNext();) {
out.writeObject(it.next());
out.writeObject(it.getValue());
}
out.writeObject(null); // null terminate map
// do not call super.doWriteObject() as code there doesn't work for reference map
}
/**
* Replaces the superclass method to read the state of this class.
* <p>
* Serialization is not one of the JDK's nicest topics. Normal serialization will
* initialise the superclass before the subclass. Sometimes however, this isn't
* what you want, as in this case the <code>put()</code> method on read can be
* affected by subclass state.
* <p>
* The solution adopted here is to deserialize the state data of this class in
* this protected method. This method must be called by the
* <code>readObject()</code> of the first serializable subclass.
* <p>
* Subclasses may override if the subclass has a specific field that must be present
* before <code>put()</code> or <code>calculateThreshold()</code> will work correctly.
*
* @param in the input stream
* @throws IOException if an error occurs while reading from the stream
* @throws ClassNotFoundException if an object read from the stream can not be loaded
*/
@Override
@SuppressWarnings("unchecked")
protected void doReadObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
this.keyType = ReferenceStrength.resolve(in.readInt());
this.valueType = ReferenceStrength.resolve(in.readInt());
this.purgeValues = in.readBoolean();
this.loadFactor = in.readFloat();
final int capacity = in.readInt();
init();
data = new HashEntry[capacity];
while (true) {
final K key = (K) in.readObject();
if (key == null) {
break;
}
final V value = (V) in.readObject();
put(key, value);
}
threshold = calculateThreshold(data.length, loadFactor);
// do not call super.doReadObject() as code there doesn't work for reference map
}
/**
* Provided protected read-only access to the key type.
* @param type the type to check against.
* @return true if keyType has the specified type
*/
protected boolean isKeyType(ReferenceStrength type) {
return this.keyType == type;
}
}