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.util.HashMap;
025import java.util.LinkedList;
026import java.util.Map;
027
028/**
029 * A cache that only remembers a given number of keys.
030 *
031 * @author Matthew Pocock
032 * @since 1.2
033 */
034
035public class FixedSizeMap implements CacheMap {
036  private Map map = new HashMap();
037  private LinkedList keys = new LinkedList();
038  private int maxSize;
039  
040  public int getMaxSize() {
041    return maxSize;
042  }
043  
044  public FixedSizeMap(int maxSize) {
045    this.maxSize = maxSize;
046  }
047  
048  public void put(Object key, Object value) {
049    if(map.containsKey(key)) {
050      keys.remove(key);
051    }
052    
053    keys.addLast(key);
054    
055    if(keys.size() > maxSize) {
056      Object k = keys.removeFirst();
057      map.remove(k);
058    }
059    map.put(key, value);
060    
061  }
062  
063  public Object get(Object key) {
064    return map.get(key);
065  }
066  
067  public void remove(Object key) {
068    map.remove(key);
069    keys.remove(key);
070  }
071}