content: /*
   * Copyright 2010, 2011, 2012 mapsforge.org
   *
   * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
   *
   * This program 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 3 of the License, or (at your option) any later version.
   *
   * This program 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 program. If not, see <http://www.gnu.org/licenses/>.
   */
  package org.oscim.utils;
  
  import java.util.LinkedHashMap;
  import java.util.Map;
  
  /**
   * An LRUCache with a fixed size and an access-order policy. Old mappings are
   * automatically removed from the cache when
   * new mappings are added. This implementation uses an {@link LinkedHashMap}
   * internally.
   *
   * @param <K> the type of the map key, see {@link Map}.
   * @param <V> the type of the map value, see {@link Map}.
   */
  public class LRUCache<K, V> extends LinkedHashMap<K, V> {
      private static final float LOAD_FACTOR = 0.6f;
      private static final long serialVersionUID = 1L;
  
      private static int calculateInitialCapacity(int capacity) {
          if (capacity < 0) {
              throw new IllegalArgumentException("capacity must not be negative: " + capacity);
          }
          return (int) (capacity / LOAD_FACTOR) + 2;
      }
  
      private final int capacity;
  
      /**
       * @param capacity the maximum capacity of this cache.
       * @throws IllegalArgumentException if the capacity is negative.
       */
      public LRUCache(int capacity) {
          super(calculateInitialCapacity(capacity), LOAD_FACTOR, true);
          this.capacity = capacity;
      }
  
      @Override
      protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
          return size() > this.capacity;
      }
  }
  