net.hasor.utils.convert.WeakFastHashMap Maven / Gradle / Ivy
/*
* 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 net.hasor.utils.convert;
import java.util.*;
/**
* A customized implementation of java.util.HashMap designed
* to operate in a multithreaded environment where the large majority of
* method calls are read-only, instead of structural changes. When operating
* in "fast" mode, read calls are non-synchronized and write calls perform the
* following steps:
*
* - Clone the existing collection
*
- Perform the modification on the clone
*
- Replace the existing collection with the (modified) clone
*
* When first created, objects of this class default to "slow" mode, where
* all accesses of any type are synchronized but no cloning takes place. This
* is appropriate for initially populating the collection, followed by a switch
* to "fast" mode (by calling setFast(true)) after initialization
* is complete.
*
* NOTE: If you are creating and accessing a
* HashMap only within a single thread, you should use
* java.util.HashMap directly (with no synchronization), for
* maximum performance.
*
* NOTE: This class is not cross-platform.
* Using it may cause unexpected failures on some architectures.
* It suffers from the same problems as the double-checked locking idiom.
* In particular, the instruction that clones the internal collection and the
* instruction that sets the internal reference to the clone can be executed
* or perceived out-of-order. This means that any read operation might fail
* unexpectedly, as it may be reading the state of the internal collection
* before the internal collection is fully formed.
* For more information on the double-checked locking idiom, see the
*
* Double-Checked Locking Idiom Is Broken Declaration.
*
* @since Commons Collections 1.0
* @version $Revision: 687089 $ $Date: 2008-08-19 17:33:30 +0100 (Tue, 19 Aug 2008) $
*
* @author Craig R. McClanahan
* @author Stephen Colebourne
*/
@SuppressWarnings({ "rawtypes", "serial", "unchecked" })
class WeakFastHashMap extends HashMap {
/** The underlying map we are managing. */
private Map map = null;
/** Are we currently operating in "fast" mode? */
private boolean fast = false;
// Constructors
// ----------------------------------------------------------------------
/** Construct an empty map. */
public WeakFastHashMap() {
super();
this.map = this.createMap();
}
/**
* Construct an empty map with the specified capacity.
* @param capacity the initial capacity of the empty map
*/
public WeakFastHashMap(final int capacity) {
super();
this.map = this.createMap(capacity);
}
/**
* Construct an empty map with the specified capacity and load factor.
* @param capacity the initial capacity of the empty map
* @param factor the load factor of the new map
*/
public WeakFastHashMap(final int capacity, final float factor) {
super();
this.map = this.createMap(capacity, factor);
}
/**
* Construct a new map with the same mappings as the specified map.
* @param map the map whose mappings are to be copied
*/
public WeakFastHashMap(final Map map) {
super();
this.map = this.createMap(map);
}
// Property access
// ----------------------------------------------------------------------
/**
* Returns true if this map is operating in fast mode.
* @return true if this map is operating in fast mode
*/
public boolean getFast() {
return this.fast;
}
/**
* Sets whether this map is operating in fast mode.
* @param fast true if this map should operate in fast mode
*/
public void setFast(final boolean fast) {
this.fast = fast;
}
// Map access
// ----------------------------------------------------------------------
// These methods can forward straight to the wrapped Map in 'fast' mode.
// (because they are query methods)
/**
* Return the value to which this map maps the specified key. Returns
* null if the map contains no mapping for this key, or if
* there is a mapping with a value of null. Use the
* containsKey() method to disambiguate these cases.
*
* @param key the key whose value is to be returned
* @return the value mapped to that key, or null
*/
@Override
public Object get(final Object key) {
if (this.fast) {
return this.map.get(key);
} else {
synchronized (this.map) {
return this.map.get(key);
}
}
}
/**
* Return the number of key-value mappings in this map.
*
* @return the current size of the map
*/
@Override
public int size() {
if (this.fast) {
return this.map.size();
} else {
synchronized (this.map) {
return this.map.size();
}
}
}
/**
* Return true if this map contains no mappings.
*
* @return is the map currently empty
*/
@Override
public boolean isEmpty() {
if (this.fast) {
return this.map.isEmpty();
} else {
synchronized (this.map) {
return this.map.isEmpty();
}
}
}
/**
* Return true if this map contains a mapping for the
* specified key.
*
* @param key the key to be searched for
* @return true if the map contains the key
*/
@Override
public boolean containsKey(final Object key) {
if (this.fast) {
return this.map.containsKey(key);
} else {
synchronized (this.map) {
return this.map.containsKey(key);
}
}
}
/**
* Return true if this map contains one or more keys mapping
* to the specified value.
*
* @param value the value to be searched for
* @return true if the map contains the value
*/
@Override
public boolean containsValue(final Object value) {
if (this.fast) {
return this.map.containsValue(value);
} else {
synchronized (this.map) {
return this.map.containsValue(value);
}
}
}
// Map modification
// ----------------------------------------------------------------------
// These methods perform special behaviour in 'fast' mode.
// The map is cloned, updated and then assigned back.
// See the comments at the top as to why this won't always work.
/**
* Associate the specified value with the specified key in this map.
* If the map previously contained a mapping for this key, the old
* value is replaced and returned.
*
* @param key the key with which the value is to be associated
* @param value the value to be associated with this key
* @return the value previously mapped to the key, or null
*/
@Override
public Object put(final Object key, final Object value) {
if (this.fast) {
synchronized (this) {
Map temp = this.cloneMap(this.map);
Object result = temp.put(key, value);
this.map = temp;
return result;
}
} else {
synchronized (this.map) {
return this.map.put(key, value);
}
}
}
/**
* Copy all of the mappings from the specified map to this one, replacing
* any mappings with the same keys.
*
* @param in the map whose mappings are to be copied
*/
@Override
public void putAll(final Map in) {
if (this.fast) {
synchronized (this) {
Map temp = this.cloneMap(this.map);
temp.putAll(in);
this.map = temp;
}
} else {
synchronized (this.map) {
this.map.putAll(in);
}
}
}
/**
* Remove any mapping for this key, and return any previously
* mapped value.
*
* @param key the key whose mapping is to be removed
* @return the value removed, or null
*/
@Override
public Object remove(final Object key) {
if (this.fast) {
synchronized (this) {
Map temp = this.cloneMap(this.map);
Object result = temp.remove(key);
this.map = temp;
return result;
}
} else {
synchronized (this.map) {
return this.map.remove(key);
}
}
}
/**
* Remove all mappings from this map.
*/
@Override
public void clear() {
if (this.fast) {
synchronized (this) {
this.map = this.createMap();
}
} else {
synchronized (this.map) {
this.map.clear();
}
}
}
// Basic object methods
// ----------------------------------------------------------------------
/**
* Compare the specified object with this list for equality. This
* implementation uses exactly the code that is used to define the
* list equals function in the documentation for the
* Map.equals method.
*
* @param o the object to be compared to this list
* @return true if the two maps are equal
*/
@Override
public boolean equals(final Object o) {
// Simple tests that require no synchronization
if (o == this) {
return true;
} else if (!(o instanceof Map)) {
return false;
}
Map mo = (Map) o;
// Compare the two maps for equality
if (this.fast) {
if (mo.size() != this.map.size()) {
return false;
}
Iterator i = this.map.entrySet().iterator();
while (i.hasNext()) {
Map.Entry e = (Map.Entry) i.next();
Object key = e.getKey();
Object value = e.getValue();
if (value == null) {
if (!(mo.get(key) == null && mo.containsKey(key))) {
return false;
}
} else {
if (!value.equals(mo.get(key))) {
return false;
}
}
}
return true;
} else {
synchronized (this.map) {
if (mo.size() != this.map.size()) {
return false;
}
Iterator i = this.map.entrySet().iterator();
while (i.hasNext()) {
Map.Entry e = (Map.Entry) i.next();
Object key = e.getKey();
Object value = e.getValue();
if (value == null) {
if (!(mo.get(key) == null && mo.containsKey(key))) {
return false;
}
} else {
if (!value.equals(mo.get(key))) {
return false;
}
}
}
return true;
}
}
}
/**
* Return the hash code value for this map. This implementation uses
* exactly the code that is used to define the list hash function in the
* documentation for the Map.hashCode method.
*
* @return suitable integer hash code
*/
@Override
public int hashCode() {
if (this.fast) {
int h = 0;
Iterator i = this.map.entrySet().iterator();
while (i.hasNext()) {
h += i.next().hashCode();
}
return h;
} else {
synchronized (this.map) {
int h = 0;
Iterator i = this.map.entrySet().iterator();
while (i.hasNext()) {
h += i.next().hashCode();
}
return h;
}
}
}
/**
* Return a shallow copy of this FastHashMap instance.
* The keys and values themselves are not copied.
*
* @return a clone of this map
*/
@Override
public Object clone() {
WeakFastHashMap results = null;
if (this.fast) {
results = new WeakFastHashMap(this.map);
} else {
synchronized (this.map) {
results = new WeakFastHashMap(this.map);
}
}
results.setFast(this.getFast());
return results;
}
// Map views
// ----------------------------------------------------------------------
/**
* Return a collection view of the mappings contained in this map. Each
* element in the returned collection is a Map.Entry.
* @return the set of map Map entries
*/
@Override
public Set entrySet() {
return new EntrySet();
}
/**
* Return a set view of the keys contained in this map.
* @return the set of the Map's keys
*/
@Override
public Set keySet() {
return new KeySet();
}
/**
* Return a collection view of the values contained in this map.
* @return the set of the Map's values
*/
@Override
public Collection values() {
return new Values();
}
// Abstractions on Map creations (for subclasses such as WeakFastHashMap)
// ----------------------------------------------------------------------
protected Map createMap() {
return new WeakHashMap();
}
protected Map createMap(final int capacity) {
return new WeakHashMap(capacity);
}
protected Map createMap(final int capacity, final float factor) {
return new WeakHashMap(capacity, factor);
}
protected Map createMap(final Map map) {
return new WeakHashMap(map);
}
protected Map cloneMap(final Map map) {
return this.createMap(map);
}
// Map view inner classes
// ----------------------------------------------------------------------
/**
* Abstract collection implementation shared by keySet(), values() and entrySet().
*/
private abstract class CollectionView implements Collection {
public CollectionView() {
}
protected abstract Collection get(Map map);
protected abstract Object iteratorNext(Map.Entry entry);
@Override
public void clear() {
if (WeakFastHashMap.this.fast) {
synchronized (WeakFastHashMap.this) {
WeakFastHashMap.this.map = WeakFastHashMap.this.createMap();
}
} else {
synchronized (WeakFastHashMap.this.map) {
this.get(WeakFastHashMap.this.map).clear();
}
}
}
@Override
public boolean remove(final Object o) {
if (WeakFastHashMap.this.fast) {
synchronized (WeakFastHashMap.this) {
Map temp = WeakFastHashMap.this.cloneMap(WeakFastHashMap.this.map);
boolean r = this.get(temp).remove(o);
WeakFastHashMap.this.map = temp;
return r;
}
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).remove(o);
}
}
}
@Override
public boolean removeAll(final Collection o) {
if (WeakFastHashMap.this.fast) {
synchronized (WeakFastHashMap.this) {
Map temp = WeakFastHashMap.this.cloneMap(WeakFastHashMap.this.map);
boolean r = this.get(temp).removeAll(o);
WeakFastHashMap.this.map = temp;
return r;
}
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).removeAll(o);
}
}
}
@Override
public boolean retainAll(final Collection o) {
if (WeakFastHashMap.this.fast) {
synchronized (WeakFastHashMap.this) {
Map temp = WeakFastHashMap.this.cloneMap(WeakFastHashMap.this.map);
boolean r = this.get(temp).retainAll(o);
WeakFastHashMap.this.map = temp;
return r;
}
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).retainAll(o);
}
}
}
@Override
public int size() {
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).size();
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).size();
}
}
}
@Override
public boolean isEmpty() {
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).isEmpty();
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).isEmpty();
}
}
}
@Override
public boolean contains(final Object o) {
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).contains(o);
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).contains(o);
}
}
}
@Override
public boolean containsAll(final Collection o) {
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).containsAll(o);
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).containsAll(o);
}
}
}
@Override
public Object[] toArray(final Object[] o) {
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).toArray(o);
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).toArray(o);
}
}
}
@Override
public Object[] toArray() {
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).toArray();
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).toArray();
}
}
}
@Override
public boolean equals(final Object o) {
if (o.equals(this)) {
return true;
}
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).equals(o);
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).equals(o);
}
}
}
@Override
public int hashCode() {
if (WeakFastHashMap.this.fast) {
return this.get(WeakFastHashMap.this.map).hashCode();
} else {
synchronized (WeakFastHashMap.this.map) {
return this.get(WeakFastHashMap.this.map).hashCode();
}
}
}
@Override
public boolean add(final Object o) {
throw new UnsupportedOperationException();
}
@Override
public boolean addAll(final Collection c) {
throw new UnsupportedOperationException();
}
@Override
public Iterator iterator() {
return new CollectionViewIterator();
}
private class CollectionViewIterator implements Iterator {
private Map expected;
private Map.Entry lastReturned = null;
private Iterator iterator;
public CollectionViewIterator() {
this.expected = WeakFastHashMap.this.map;
this.iterator = this.expected.entrySet().iterator();
}
@Override
public boolean hasNext() {
if (this.expected != WeakFastHashMap.this.map) {
throw new ConcurrentModificationException();
}
return this.iterator.hasNext();
}
@Override
public Object next() {
if (this.expected != WeakFastHashMap.this.map) {
throw new ConcurrentModificationException();
}
this.lastReturned = (Map.Entry) this.iterator.next();
return CollectionView.this.iteratorNext(this.lastReturned);
}
@Override
public void remove() {
if (this.lastReturned == null) {
throw new IllegalStateException();
}
if (WeakFastHashMap.this.fast) {
synchronized (WeakFastHashMap.this) {
if (this.expected != WeakFastHashMap.this.map) {
throw new ConcurrentModificationException();
}
WeakFastHashMap.this.remove(this.lastReturned.getKey());
this.lastReturned = null;
this.expected = WeakFastHashMap.this.map;
}
} else {
this.iterator.remove();
this.lastReturned = null;
}
}
}
}
/**
* Set implementation over the keys of the FastHashMap
*/
private class KeySet extends CollectionView implements Set {
@Override
protected Collection get(final Map map) {
return map.keySet();
}
@Override
protected Object iteratorNext(final Map.Entry entry) {
return entry.getKey();
}
}
/**
* Collection implementation over the values of the FastHashMap
*/
private class Values extends CollectionView {
@Override
protected Collection get(final Map map) {
return map.values();
}
@Override
protected Object iteratorNext(final Map.Entry entry) {
return entry.getValue();
}
}
/**
* Set implementation over the entries of the FastHashMap
*/
private class EntrySet extends CollectionView implements Set {
@Override
protected Collection get(final Map map) {
return map.entrySet();
}
@Override
protected Object iteratorNext(final Map.Entry entry) {
return entry;
}
}
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