package org.djutils.immutablecollections;
   
   import java.util.HashMap;
   import java.util.HashSet;
   import java.util.Map;
   import java.util.Map.Entry;
   import java.util.Set;
   
   /**
   * An immutable wrapper for a HashMap.
   * <p>
   * Copyright (c) 2016-2019 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See
   * for project information <a href="https://djutils.org" target="_blank"> https://djutils.org</a>. The DJUTILS project is
   * distributed under a three-clause BSD-style license, which can be found at
   * <a href="https://djutils.org/docs/license.html" target="_blank"> https://djutils.org/docs/license.html</a>.
   * </p>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://www.tudelft.nl/staff/p.knoppers/">Peter Knoppers</a>
   * @author <a href="https://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   * @param <K> the key type of content of this Map
   * @param <V> the value type of content of this Map
   */
  public class ImmutableHashMap<K, V> extends ImmutableAbstractMap<K, V>
  {
      /** */
      private static final long serialVersionUID = 20160507L;
  
      /** the cached keySet. */
      private ImmutableSet<K> cachedKeySet = null;
  
      /** the cached entrySet. */
      private ImmutableSet<ImmutableEntry<K, V>> cachedEntrySet = null;
  
      /**
       * @param map Map&lt;K,V&gt;; the map to use for the immutable map.
       */
      public ImmutableHashMap(final Map<K, V> map)
      {
          super(new HashMap<K, V>(map), Immutable.COPY);
      }
  
      /**
       * @param map Map&lt;K,V&gt;; the map to use for the immutable map.
       * @param copyOrWrap COPY stores a safe, internal copy of the collection; WRAP stores a pointer to the original collection
       */
      public ImmutableHashMap(final Map<K, V> map, final Immutable copyOrWrap)
      {
          super(copyOrWrap == Immutable.COPY ? new HashMap<K, V>(map) : map, copyOrWrap);
      }
  
      /**
       * @param immutableMap ImmutableAbstractMap&lt;K,V&gt;; the map to use for the immutable map.
       */
      public ImmutableHashMap(final ImmutableAbstractMap<K, V> immutableMap)
      {
          super(new HashMap<K, V>(immutableMap.getMap()), Immutable.COPY);
      }
  
      /**
       * @param immutableMap ImmutableAbstractMap&lt;K,V&gt;; the map to use for the immutable map.
       * @param copyOrWrap COPY stores a safe, internal copy of the collection; WRAP stores a pointer to the original collection
       */
      public ImmutableHashMap(final ImmutableAbstractMap<K, V> immutableMap, final Immutable copyOrWrap)
      {
          super(copyOrWrap == Immutable.COPY ? new HashMap<K, V>(immutableMap.getMap()) : immutableMap.getMap(), copyOrWrap);
      }
  
      /** {@inheritDoc} */
      @Override
      protected final Map<K, V> getMap()
      {
          return super.getMap();
      }
  
      /** {@inheritDoc} */
      @Override
      public final Map<K, V> toMap()
      {
          return new HashMap<K, V>(getMap());
      }
  
      /** {@inheritDoc} */
      @Override
      public final ImmutableSet<K> keySet()
      {
          if (this.cachedKeySet == null)
          {
              Set<K> immutableKeySet = new HashSet<>(getMap().keySet());
              this.cachedKeySet = new ImmutableHashSet<>(immutableKeySet, Immutable.WRAP);
          }
          return this.cachedKeySet;
      }
  
      /** {@inheritDoc} */
      @Override
      public ImmutableSet<ImmutableEntry<K, V>> entrySet()
      {
          if (this.cachedEntrySet == null)
          {
             Set<ImmutableEntry<K, V>> immutableEntrySet = new HashSet<>();
             for (Entry<K, V> entry : getMap().entrySet())
             {
                 immutableEntrySet.add(new ImmutableEntry<>(entry));
             }
             this.cachedEntrySet = new ImmutableHashSet<>(immutableEntrySet, Immutable.WRAP);
         }
         return this.cachedEntrySet;
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public String toString()
     {
         Map<K, V> map = getMap();
         if (null == map)
         {
             return "ImmutableHashMap []";
         }
         return "ImmutableHashMap [" + map.toString() + "]";
     }
 
 }