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package de.lmu.ifi.dbs.elki.utilities.datastructures;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2011
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
/**
* Multi-Associative container, that stores a list of values for a particular key.
*
* @author Erich Schubert
*
* @apiviz.has List oneway - - contains
*
* @param <K> Key type
* @param <V> Value type
*/
// TODO: use MultiValueMap from apache collections instead?
public class HashMapList<K, V> extends HashMap<K, List<V>> {
/**
* Serial version
*/
private static final long serialVersionUID = 3883242025598456055L;
/**
* Constructor.
*/
public HashMapList() {
super();
}
/**
* Constructor with initial capacity (of the hash)
*
* @param initialCapacity initial capacity
*/
public HashMapList(int initialCapacity) {
super(initialCapacity);
}
/**
* Add a single value to the given key.
*
* @param key Key
* @param value Additional Value
*/
public synchronized void add(K key, V value) {
List<V> list = super.get(key);
if (list == null) {
list = new ArrayList<V>(1);
super.put(key, list);
}
list.add(value);
}
/**
* Check that there is at least one value for the key.
*/
@Override
public boolean containsKey(Object key) {
List<V> list = super.get(key);
if (list == null) {
return false;
}
return list.size() > 0;
}
/**
* Remove a single value from the map.
*
* @param key Key to remove
* @param value Value to remove.
* @return <tt>true</tt> if this list contained the specified element
*/
public synchronized boolean remove(K key, V value) {
List<V> list = super.get(key);
if (list == null) {
return false;
}
boolean success = list.remove(value);
// remove empty lists.
if (list.size() == 0) {
super.remove(key);
}
return success;
}
/**
* Test if a given value is already present for the key.
*
* @param key Key
* @param value Value
* @return <tt>true</tt> if the keys list contains the specified element
*/
public boolean contains(K key, V value) {
List<V> list = super.get(key);
if (list == null) {
return false;
}
return list.contains(value);
}
}
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