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Relational Persistence for Java
//$Id: FastHashMap.java 3890 2004-06-03 16:31:32Z steveebersole $
/*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999-2002 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [email protected].
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* 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.
* 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
*
* 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.
*
*/
public final class FastHashMap implements Map, Serializable {
// ----------------------------------------------------------- Constructors
/**
* Construct a an empty map.
*/
public FastHashMap() {
super();
this.map = new HashMap();
}
/**
* Construct an empty map with the specified capacity.
*
* @param capacity The initial capacity of the empty map
*/
public FastHashMap(int capacity) {
super();
this.map = new HashMap(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 FastHashMap(int capacity, float factor) {
super();
this.map = new HashMap(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 FastHashMap(Map map) {
super();
this.map = new HashMap(map);
}
// ----------------------------------------------------- Instance Variables
/**
* The underlying map we are managing.
*/
private HashMap map = null;
// --------------------------------------------------------- Public Methods
/**
* Remove all mappings from this map.
*/
public void clear() {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
temp.clear();
map = temp;
}
}
/**
* Return a shallow copy of this FastHashMap instance.
* The keys and values themselves are not copied.
*/
public Object clone() {
return new FastHashMap(map);
}
/**
* Return true if this map contains a mapping for the
* specified key.
*
* @param key Key to be searched for
*/
public boolean containsKey(Object key) {
return map.containsKey(key);
}
/**
* Return true if this map contains one or more keys mapping
* to the specified value.
*
* @param value Value to be searched for
*/
public boolean containsValue(Object value) {
return map.containsValue(value);
}
/**
* Return a collection view of the mappings contained in this map. Each
* element in the returned collection is a Map.Entry.
*/
public Set entrySet() {
return map.entrySet();
}
/**
* 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 Object to be compared to this list
*/
public boolean equals(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 ( mo.size() != map.size() )
return false;
java.util.Iterator i = 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 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 Key whose value is to be returned
*/
public Object get(Object key) {
return map.get(key);
}
/**
* 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.
*/
public int hashCode() {
int h = 0;
java.util.Iterator i = map.entrySet().iterator();
while ( i.hasNext() )
h += i.next().hashCode();
return h;
}
/**
* Return true if this map contains no mappings.
*/
public boolean isEmpty() {
return map.isEmpty();
}
/**
* Return a set view of the keys contained in this map.
*/
public Set keySet() {
return map.keySet();
}
/**
* 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
*/
public Object put(Object key, Object value) {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
Object result = temp.put(key, value);
map = temp;
return (result);
}
}
/**
* Copy all of the mappings from the specified map to this one, replacing
* any mappings with the same keys.
*
* @param in Map whose mappings are to be copied
*/
public void putAll(Map in) {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
temp.putAll(in);
map = temp;
}
}
/**
* Remove any mapping for this key, and return any previously
* mapped value.
*
* @param key Key whose mapping is to be removed
*/
public Object remove(Object key) {
synchronized (this) {
HashMap temp = (HashMap) map.clone();
Object result = temp.remove(key);
map = temp;
return (result);
}
}
/**
* Return the number of key-value mappings in this map.
*/
public int size() {
return map.size();
}
/**
* Return a collection view of the values contained in this map.
*/
public Collection values() {
return map.values();
}
public String toString() { return map.toString(); }
}
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