001/*
002 *                    BioJava development code
003 *
004 * This code may be freely distributed and modified under the
005 * terms of the GNU Lesser General Public Licence.  This should
006 * be distributed with the code.  If you do not have a copy,
007 * see:
008 *
009 *      http://www.gnu.org/copyleft/lesser.html
010 *
011 * Copyright for this code is held jointly by the individual
012 * authors.  These should be listed in @author doc comments.
013 *
014 * For more information on the BioJava project and its aims,
015 * or to join the biojava-l mailing list, visit the home page
016 * at:
017 *
018 *      http://www.biojava.org/
019 *
020 */
021
022package org.biojava.utils.cache;
023
024import java.lang.ref.Reference;
025import java.lang.ref.WeakReference;
026import java.util.HashMap;
027import java.util.Map;
028
029/**
030 * A cache which retains weak references to objects
031 *
032 * @since 1.3
033 * @author Thomas Down
034 */
035
036public class WeakCacheMap implements CacheMap {
037  private Map map = new HashMap();
038  
039  public void put(Object key, Object value) {
040      map.put(key, new WeakReference(value));
041  }
042  
043  public Object get(Object key) {
044      Reference ref = (Reference) map.get(key);
045      if (ref != null) {
046          return ref.get();
047      } else {
048          return null;
049      }
050  }
051  
052  public void remove(Object key) {
053    map.remove(key);
054  }
055}