/*
 *                    BioJava development code
 *
 * This code may be freely distributed and modified under the
 * terms of the GNU Lesser General Public Licence.  This should
 * be distributed with the code.  If you do not have a copy,
 * see:
 *
 *      http://www.gnu.org/copyleft/lesser.html
 *
 * Copyright for this code is held jointly by the individual
 * authors.  These should be listed in @author doc comments.
 *
 * For more information on the BioJava project and its aims,
 * or to join the biojava-l mailing list, visit the home page
 * at:
 *
 *      http://www.biojava.org/
 *
 */

package org.biojava.utils.cache;

import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;

/**
 * A cache that only remembers a given number of keys.
 *
 * @author Matthew Pocock
 * @since 1.2
 */

public class FixedSizeMap implements CacheMap {
  private Map map = new HashMap();
  private LinkedList keys = new LinkedList();
  private int maxSize;
  
  public int getMaxSize() {
    return maxSize;
  }
  
  public FixedSizeMap(int maxSize) {
    this.maxSize = maxSize;
  }
  
  public void put(Object key, Object value) {
    if(map.containsKey(key)) {
      keys.remove(key);
    }
    
    keys.addLast(key);
    
    if(keys.size() > maxSize) {
      Object k = keys.removeFirst();
      map.remove(k);
    }
    map.put(key, value);
    
  }
  
  public Object get(Object key) {
    return map.get(key);
  }
  
  public void remove(Object key) {
    map.remove(key);
    keys.remove(key);
  }
}