content: /*
   * This library is part of OpenCms -
   * the Open Source Content Management System
   *
   * Copyright (c) Alkacon Software GmbH & Co. KG (https://www.alkacon.com)
   *
   * 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.
   *
   * For further information about Alkacon Software, please see the
   * company website: https://www.alkacon.com
   *
   * For further information about OpenCms, please see the
   * project website: https://www.opencms.org
   *
   * 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
   */
  
  package org.opencms.util;
  
  import java.util.Collections;
  import java.util.Map;
  import java.util.Set;
  
  import com.google.common.collect.HashMultimap;
  import com.google.common.collect.Maps;
  import com.google.common.collect.Multimap;
  import com.google.common.collect.Multimaps;
  
  /**
   * Special collection class which allows lookup from keys to values  and from values to sets of keys.<p>
   *
   * It also  implements efficient removal of values, not just keys.<p>
   *
   * @param <K> the key type
   * @param <V> the value type
   */
  public class CmsManyToOneMap<K, V> {
  
      /** Map from keys to values . */
      private Map<K, V> m_forwardMap = Maps.newHashMap();
  
      /** Map from values to sets of keys. */
      private HashMultimap<V, K> m_reverseMap = HashMultimap.create();
  
      /**
       * Creates a new instance.<p>
       */
      public CmsManyToOneMap() {
  
          // do nothing
      }
  
      /**
       * Creates a new instance by copying the data from another one.<p>
       *
       * @param other the other map to copy the data from
       */
      public CmsManyToOneMap(CmsManyToOneMap<K, V> other) {
  
          for (Map.Entry<K, V> entry : other.getForwardMap().entrySet()) {
              put(entry.getKey(), entry.getValue());
          }
      }
  
      /**
       * Gets the value for a key.<p>
       *
       * @param key the key
       * @return the value for the key, or null
       */
      public V get(K key) {
  
          return m_forwardMap.get(key);
      }
  
      /**
       * Associates a value with a key.<p>
       *
       * @param key the key
       * @param value the value
       */
      public void put(K key, V value) {
  
          m_forwardMap.put(key, value);
          m_reverseMap.put(value, key);
  
      }
  
      /**
       * Removes the entry with the given key.<p>
       *
       * @param key the key
       */
      public void remove(K key) {
  
          V removedValue = m_forwardMap.remove(key);
          if (removedValue != null) {
              m_reverseMap.remove(removedValue, key);
          }
      }
  
      /**
       * Removes all entries with the given value.<p>
       *
       * @param value the value
       */
      public void removeValue(V value) {
  
          Set<K> keys = m_reverseMap.removeAll(value);
          for (K key : keys) {
              m_forwardMap.remove(key);
          }
      }
  
      /**
       * Gets the (immutable) map from keys to values.
       *
       * @return the map from keys to values
       */
      Map<K, V> getForwardMap() {
  
          return Collections.unmodifiableMap(m_forwardMap);
      }
  
      /**
       * Gets the multimap from values to keys.<p>
       *
       * @return the multimap from values to keys
       */
      Multimap<V, K> getReverseMap() {
  
          return Multimaps.unmodifiableSetMultimap(m_reverseMap);
      }
  }
  