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      1 /*
      2  * Copyright (C) 2007 Google Inc.
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.google.common.collect;
     18 
     19 import static com.google.common.base.Preconditions.checkArgument;
     20 
     21 import java.io.IOException;
     22 import java.io.ObjectInputStream;
     23 import java.io.ObjectOutputStream;
     24 import java.util.EnumMap;
     25 import java.util.Map;
     26 
     27 /**
     28  * A {@code BiMap} backed by two {@code EnumMap} instances. Null keys and values
     29  * are not permitted. An {@code EnumBiMap} and its inverse are both
     30  * serializable.
     31  *
     32  * @author Mike Bostock
     33  * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
     34  */
     35 public final class EnumBiMap<K extends Enum<K>, V extends Enum<V>>
     36     extends AbstractBiMap<K, V> {
     37   private transient Class<K> keyType;
     38   private transient Class<V> valueType;
     39 
     40   /**
     41    * Returns a new, empty {@code EnumBiMap} using the specified key and value
     42    * types.
     43    *
     44    * @param keyType the key type
     45    * @param valueType the value type
     46    */
     47   public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V>
     48       create(Class<K> keyType, Class<V> valueType) {
     49     return new EnumBiMap<K, V>(keyType, valueType);
     50   }
     51 
     52   /**
     53    * Returns a new bimap with the same mappings as the specified map. If the
     54    * specified map is an {@code EnumBiMap}, the new bimap has the same types as
     55    * the provided map. Otherwise, the specified map must contain at least one
     56    * mapping, in order to determine the key and value types.
     57    *
     58    * @param map the map whose mappings are to be placed in this map
     59    * @throws IllegalArgumentException if map is not an {@code EnumBiMap}
     60    *     instance and contains no mappings
     61    */
     62   public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V>
     63       create(Map<K, V> map) {
     64     EnumBiMap<K, V> bimap = create(inferKeyType(map), inferValueType(map));
     65     bimap.putAll(map);
     66     return bimap;
     67   }
     68 
     69   private EnumBiMap(Class<K> keyType, Class<V> valueType) {
     70     super(new EnumMap<K, V>(keyType), new EnumMap<V, K>(valueType));
     71     this.keyType = keyType;
     72     this.valueType = valueType;
     73   }
     74 
     75   static <K extends Enum<K>> Class<K> inferKeyType(Map<K, ?> map) {
     76     if (map instanceof EnumBiMap) {
     77       return ((EnumBiMap<K, ?>) map).keyType();
     78     }
     79     if (map instanceof EnumHashBiMap) {
     80       return ((EnumHashBiMap<K, ?>) map).keyType();
     81     }
     82     checkArgument(!map.isEmpty());
     83     return map.keySet().iterator().next().getDeclaringClass();
     84   }
     85 
     86   private static <V extends Enum<V>> Class<V> inferValueType(Map<?, V> map) {
     87     if (map instanceof EnumBiMap) {
     88       return ((EnumBiMap<?, V>) map).valueType;
     89     }
     90     checkArgument(!map.isEmpty());
     91     return map.values().iterator().next().getDeclaringClass();
     92   }
     93 
     94   /** Returns the associated key type. */
     95   public Class<K> keyType() {
     96     return keyType;
     97   }
     98 
     99   /** Returns the associated value type. */
    100   public Class<V> valueType() {
    101     return valueType;
    102   }
    103 
    104   /**
    105    * @serialData the key class, value class, number of entries, first key, first
    106    *     value, second key, second value, and so on.
    107    */
    108   private void writeObject(ObjectOutputStream stream) throws IOException {
    109     stream.defaultWriteObject();
    110     stream.writeObject(keyType);
    111     stream.writeObject(valueType);
    112     Serialization.writeMap(this, stream);
    113   }
    114 
    115   @SuppressWarnings("unchecked") // reading fields populated by writeObject
    116   private void readObject(ObjectInputStream stream)
    117       throws IOException, ClassNotFoundException {
    118     stream.defaultReadObject();
    119     keyType = (Class<K>) stream.readObject();
    120     valueType = (Class<V>) stream.readObject();
    121     setDelegates(new EnumMap<K, V>(keyType), new EnumMap<V, K>(valueType));
    122     Serialization.populateMap(this, stream);
    123   }
    124 
    125   private static final long serialVersionUID = 0;
    126 }
    127