Multi Map : Customized Map « Collections Data Structure « Java

1. Java
2. Collections Data Structure
3. Customized Map

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
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * 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;
   @SuppressWarnings("unchecked")
   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() {
    map.clear();
  }
  public void add(K k, V v) {
    Collection<V> s = map.get(k);
    if (s == null) {
      s = makeCollection();
      map.put(k, s);
    }
    s.add(v);
  }
  public void remove(K k, V v) {
    Collection<V> s = map.get(k);
    if (s != null) {
      s.remove(v);
      if (s.isEmpty()) map.remove(k);
    }
  }
  public void removeAll(K k) {
    map.remove(k);
  }
  public Collection<V> get(K k) {
    Collection<V> s = map.get(k);
    if (s != null) return s;
    return Collections.<V>emptySet();
    }

}

   
    
    
    
  

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