Multi Map : Customized Map « Collections Data Structure « Java

Multi Map

 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2006, University of Maryland
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

 * @author pugh
public class MultiMap<K,  V> {
  final Class<? extends Collection<V>> containerClass;
   public  MultiMap(Class<? extends Collection> c) {
    containerClass = (Class<? extends Collection<V>>) c;
  private Collection<V> makeCollection() {
    try {
      return containerClass.newInstance();
    } catch (InstantiationException e) {
      throw new RuntimeException(e);
    } catch (IllegalAccessException e) {
      throw new RuntimeException(e);
  Map<K,  Collection<V>> map = new HashMap<K,  Collection<V>>();
  public Collection<? extends K> keySet() {
    return map.keySet();
  public void clear() {
  public void add(K k, V v) {
    Collection<V> s = map.get(k);
    if (s == null) {
      s = makeCollection();
      map.put(k, s);
  public void remove(K k, V v) {
    Collection<V> s = map.get(k);
    if (s != null) {
      if (s.isEmpty()) map.remove(k);
  public void removeAll(K k) {
  public Collection<V> get(K k) {
    Collection<V> s = map.get(k);
    if (s != null) return s;
    return Collections.<V>emptySet();



Related examples in the same category

1.Ordered Map
2.Case Insensitive Map
3.A Map collection with real-time behavior
4.Cache Map
5.Map implementation Optimized for Strings keys
6.An integer hashmap
7.An IdentityMap that uses reference-equality instead of object-equality
8.Int Object HashMap
9.Concurrent Skip List Map
10.A hash map that uses primitive ints for the key rather than objects.
11.Integer Map
12.Copy On Write Map
13.Expiring Map
14.Array Map
15.Int Object HashMap (from CERN)
16.Int HashMap from
17.String Map
18.List Map
19.Map using Locale objects as keys
20.Map with keys iterated in insertion order
21.Most Recently Used Map
22.MultiMap is a Java version of the C++ STL class std::multimap
23.Object Int Map
24.Sequenced HashMap
25.Int Int Map
26.Int Object Map
27.Identity HashMap
28.A java.util.Map interface which can only hold a single object
29.A multi valued Map
30.A simple hashmap from keys to integers
31.A memory-efficient hash map.
32.An implementation of the java.util.Map interface which can only hold a single object.
33.Utility methods for operating on memory-efficient maps.
34.CaseBlindHashMap - a HashMap extension, using Strings as key values.
35.A fixed size map implementation.
36.Int HashMap
37.IntMap provides a simple hashmap from keys to integers
38.Complex Key HashMap
39.A Map with multiple values for a key
40.A Map that accepts int or Integer keys only
41.A Map where keys are compared by object identity, rather than equals()
42.Type-safe Map, from char array to String value
43.A hashtable-based Map implementation with soft keys
44.List ordered map
45.Hash map using String values as keys mapped to primitive int values.
46.Lookup table that stores a list of strings
47.HashNMap stores multiple values by a single key value. Values can be retrieved using a direct query or by creating an enumeration over the stored elements.
48.Combines multiple values to form a single composite key. MultiKey can often be used as an alternative to nested maps.