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/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001-2004 The Apache Software Foundation. All rights
* reserved.
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* 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.
*
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* distribution.
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* any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
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* 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
* MultiHashMap is the default implementation of the
* {@link org.apache.commons.collections.MultiMap MultiMap} interface.
*
* A MultiMap is a Map with slightly different semantics.
* Putting a value into the map will add the value to a Collection at that
* key. Getting a value will always return a Collection, holding all the
* values put to that key. This implementation uses an ArrayList as the
* collection.
*
* For example:
*
* MultiMap mhm = new MultiHashMap();
* mhm.put(key, "A");
* mhm.put(key, "B");
* mhm.put(key, "C");
* Collection coll = mhm.get(key);
*
* coll will be a list containing "A", "B", "C".
*
* @since Commons Collections 2.0
* @version $Revision: 1.14 $ $Date: 2004/01/14 21:43:03 $
*
* @author Christopher Berry
* @author James Strachan
* @author Steve Downey
* @author Stephen Colebourne
* @author Julien Buret
* @author Serhiy Yevtushenko
*/
public class MultiHashMap extends HashMap implements MultiMap {
//backed values collection
private transient Collection values = null;
// compatibility with commons-collection releases 2.0/2.1
private static final long serialVersionUID = 1943563828307035349L;
/**
* Constructor.
*/
public MultiHashMap() {
super();
}
/**
* Constructor.
*
* @param initialCapacity the initial map capacity
*/
public MultiHashMap(int initialCapacity) {
super(initialCapacity);
}
/**
* Constructor.
*
* @param initialCapacity the initial map capacity
* @param loadFactor the amount 0.0-1.0 at which to resize the map
*/
public MultiHashMap(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
}
/**
* Constructor.
*
* @param mapToCopy a Map to copy
*/
public MultiHashMap(Map mapToCopy) {
super(mapToCopy);
}
/**
* Read the object during deserialization.
*/
private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
// This method is needed because the 1.2/1.3 Java deserialisation called
// put and thus messed up that method
// default read object
s.defaultReadObject();
// problem only with jvm <1.4
String version = "1.2";
try {
version = System.getProperty("java.version");
} catch (SecurityException ex) {
// ignore and treat as 1.2/1.3
}
if (version.startsWith("1.2") || version.startsWith("1.3")) {
for (Iterator iterator = entrySet().iterator(); iterator.hasNext();) {
Map.Entry entry = (Map.Entry) iterator.next();
// put has created a extra collection level, remove it
super.put(entry.getKey(), ((Collection) entry.getValue()).iterator().next());
}
}
}
/**
* Put a key and value into the map.
*
* The value is added to a collection mapped to the key instead of
* replacing the previous value.
*
* @param key the key to set
* @param value the value to set the key to
* @return the value added if the add is successful, null otherwise
*/
public Object put(Object key, Object value) {
// NOTE:: put is called during deserialization in JDK < 1.4 !!!!!!
// so we must have a readObject()
Collection coll = (Collection) super.get(key);
if (coll == null) {
coll = createCollection(null);
super.put(key, coll);
}
boolean results = coll.add(value);
return (results ? value : null);
}
/**
* Does the map contain a specific value.
*
* This searches the collection mapped to each key, and thus could be slow.
*
* @param value the value to search for
* @return true if the list contains the value
*/
public boolean containsValue(Object value) {
Set pairs = super.entrySet();
if (pairs == null) {
return false;
}
Iterator pairsIterator = pairs.iterator();
while (pairsIterator.hasNext()) {
Map.Entry keyValuePair = (Map.Entry) pairsIterator.next();
Collection coll = (Collection) keyValuePair.getValue();
if (coll.contains(value)) {
return true;
}
}
return false;
}
/**
* Removes a specific value from map.
*
* The item is removed from the collection mapped to the specified key.
*
* @param key the key to remove from
* @param item the value to remove
* @return the value removed (which was passed in)
*/
public Object remove(Object key, Object item) {
Collection valuesForKey = (Collection) super.get(key);
if (valuesForKey == null) {
return null;
}
valuesForKey.remove(item);
// remove the list if it is now empty
// (saves space, and allows equals to work)
if (valuesForKey.isEmpty()){
remove(key);
}
return item;
}
/**
* Clear the map.
*
* This clears each collection in the map, and so may be slow.
*/
public void clear() {
// For gc, clear each list in the map
Set pairs = super.entrySet();
Iterator pairsIterator = pairs.iterator();
while (pairsIterator.hasNext()) {
Map.Entry keyValuePair = (Map.Entry) pairsIterator.next();
Collection coll = (Collection) keyValuePair.getValue();
coll.clear();
}
super.clear();
}
/**
* Gets a view over all the values in the map.
*
* The values view includes all the entries in the collections at each map key.
*
* @return the collection view of all the values in the map
*/
public Collection values() {
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
/**
* Inner class to view the elements.
*/
private class Values extends AbstractCollection {
public Iterator iterator() {
return new ValueIterator();
}
public int size() {
int compt = 0;
Iterator it = iterator();
while (it.hasNext()) {
it.next();
compt++;
}
return compt;
}
public void clear() {
MultiHashMap.this.clear();
}
}
/**
* Inner iterator to view the elements.
*/
private class ValueIterator implements Iterator {
private Iterator backedIterator;
private Iterator tempIterator;
private ValueIterator() {
backedIterator = MultiHashMap.super.values().iterator();
}
private boolean searchNextIterator() {
while (tempIterator == null || tempIterator.hasNext() == false) {
if (backedIterator.hasNext() == false) {
return false;
}
tempIterator = ((Collection) backedIterator.next()).iterator();
}
return true;
}
public boolean hasNext() {
return searchNextIterator();
}
public Object next() {
if (searchNextIterator() == false) {
throw new NoSuchElementException();
}
return tempIterator.next();
}
public void remove() {
if (tempIterator == null) {
throw new IllegalStateException();
}
tempIterator.remove();
}
}
/**
* Clone the map.
*
* The clone will shallow clone the collections as well as the map.
*
* @return the cloned map
*/
public Object clone() {
MultiHashMap obj = (MultiHashMap) super.clone();
// clone each Collection container
for (Iterator it = entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
Collection coll = (Collection) entry.getValue();
Collection newColl = createCollection(coll);
entry.setValue(newColl);
}
return obj;
}
/**
* Creates a new instance of the map value Collection container.
*
* This method can be overridden to use your own collection type.
*
* @param coll the collection to copy, may be null
* @return the new collection
*/
protected Collection createCollection(Collection coll) {
if (coll == null) {
return new ArrayList();
} else {
return new ArrayList(coll);
}
}
}