001/*-------------------------------------------------------------------------+
002|                                                                          |
003| Copyright 2005-2011 The ConQAT Project                                   |
004|                                                                          |
005| Licensed under the Apache License, Version 2.0 (the "License");          |
006| you may not use this file except in compliance with the License.         |
007| You may obtain a copy of the License at                                  |
008|                                                                          |
009|    http://www.apache.org/licenses/LICENSE-2.0                            |
010|                                                                          |
011| Unless required by applicable law or agreed to in writing, software      |
012| distributed under the License is distributed on an "AS IS" BASIS,        |
013| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
014| See the License for the specific language governing permissions and      |
015| limitations under the License.                                           |
016+-------------------------------------------------------------------------*/
017package org.conqat.lib.commons.collections;
018
019import java.util.IdentityHashMap;
020import java.util.Map;
021
022/**
023 * A map using (unordered) pairs as key which are compared by reference.
024 * 
025 * @author hummelb
026 */
027public class IdentityPairMap<T, V> {
028
029        /** Internal storage. */
030        private final Map<T, Map<T, V>> map = new IdentityHashMap<T, Map<T, V>>();
031
032        /** Adds the given value for the given pair. */
033        public void put(ImmutablePair<T, T> pair, V value) {
034                put(pair.getFirst(), pair.getSecond(), value);
035        }
036
037        /** Adds the given value for the given pair. */
038        public void put(T t1, T t2, V value) {
039                insert(t1, t2, value);
040                insert(t2, t1, value);
041        }
042
043        /** Helper method for insertion */
044        private void insert(T t1, T t2, V value) {
045                Map<T, V> m = map.get(t1);
046                if (m == null) {
047                        m = new IdentityHashMap<T, V>();
048                        map.put(t1, m);
049                }
050                m.put(t2, value);
051        }
052
053        /** Returns whether the pair is contained. */
054        public boolean contains(ImmutablePair<T, T> pair) {
055                return contains(pair.getFirst(), pair.getSecond());
056        }
057
058        /** Returns whether the pair (t1, t2) is contained. */
059        public boolean contains(T t1, T t2) {
060                Map<T, V> m = map.get(t1);
061                if (m == null) {
062                        return false;
063                }
064                return m.containsKey(t2);
065        }
066
067        /**
068         * Returns the element stored at the pair or <code>null</code> if not
069         * stored.
070         */
071        public V get(ImmutablePair<T, T> pair) {
072                return get(pair.getFirst(), pair.getSecond());
073        }
074
075        /**
076         * Returns the element stored at pair (t1, t2) or <code>null</code> if not
077         * stored.
078         */
079        public V get(T t1, T t2) {
080                Map<T, V> m = map.get(t1);
081                if (m == null) {
082                        return null;
083                }
084                return m.get(t2);
085        }
086
087        /** Clears the map. */
088        public void clear() {
089                map.clear();
090        }
091}