001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect;
018
019import static com.google.common.base.Preconditions.checkNotNull;
020import static java.util.Objects.requireNonNull;
021
022import com.google.common.annotations.GwtCompatible;
023import com.google.common.annotations.GwtIncompatible;
024import com.google.common.annotations.J2ktIncompatible;
025import com.google.errorprone.annotations.CanIgnoreReturnValue;
026import java.io.IOException;
027import java.io.ObjectInputStream;
028import java.io.ObjectOutputStream;
029import java.util.EnumMap;
030import java.util.HashMap;
031import java.util.Map;
032import org.jspecify.annotations.Nullable;
033
034/**
035 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and a {@code HashMap}
036 * instance for values-to-keys. Null keys are not permitted, but null values are. An {@code
037 * EnumHashBiMap} and its inverse are both serializable.
038 *
039 * <p>See the Guava User Guide article on <a href=
040 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">{@code BiMap}</a>.
041 *
042 * @author Mike Bostock
043 * @since 2.0
044 */
045@GwtCompatible(emulated = true)
046@J2ktIncompatible
047public final class EnumHashBiMap<K extends Enum<K>, V extends @Nullable Object>
048    extends AbstractBiMap<K, V> {
049  transient Class<K> keyTypeOrObjectUnderJ2cl;
050
051  /**
052   * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
053   *
054   * @param keyType the key type
055   */
056  public static <K extends Enum<K>, V extends @Nullable Object> EnumHashBiMap<K, V> create(
057      Class<K> keyType) {
058    return new EnumHashBiMap<>(keyType);
059  }
060
061  /**
062   * Constructs a new bimap with the same mappings as the specified map. If the specified map is an
063   * {@code EnumHashBiMap} or an {@link EnumBiMap}, the new bimap has the same key type as the input
064   * bimap. Otherwise, the specified map must contain at least one mapping, in order to determine
065   * the key type.
066   *
067   * @param map the map whose mappings are to be placed in this map
068   * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an {@code EnumHashBiMap}
069   *     instance and contains no mappings
070   */
071  public static <K extends Enum<K>, V extends @Nullable Object> EnumHashBiMap<K, V> create(
072      Map<K, ? extends V> map) {
073    EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyTypeOrObjectUnderJ2cl(map));
074    bimap.putAll(map);
075    return bimap;
076  }
077
078  private EnumHashBiMap(Class<K> keyType) {
079    super(new EnumMap<K, V>(keyType), new HashMap<V, K>());
080    // TODO: cpovirk - Pre-size the HashMap based on the number of enum values?
081    this.keyTypeOrObjectUnderJ2cl = keyType;
082  }
083
084  // Overriding these 3 methods to show that values may be null (but not keys)
085
086  @Override
087  K checkKey(K key) {
088    return checkNotNull(key);
089  }
090
091  @CanIgnoreReturnValue
092  @Override
093  @SuppressWarnings("RedundantOverride") // b/192446478: RedundantOverride ignores some annotations.
094  // TODO(b/192446998): Remove this override after tools understand nullness better.
095  public @Nullable V put(K key, @ParametricNullness V value) {
096    return super.put(key, value);
097  }
098
099  @CanIgnoreReturnValue
100  @Override
101  @SuppressWarnings("RedundantOverride") // b/192446478: RedundantOverride ignores some annotations.
102  // TODO(b/192446998): Remove this override after tools understand nullness better.
103  public @Nullable V forcePut(K key, @ParametricNullness V value) {
104    return super.forcePut(key, value);
105  }
106
107  /** Returns the associated key type. */
108  @GwtIncompatible
109  public Class<K> keyType() {
110    return keyTypeOrObjectUnderJ2cl;
111  }
112
113  /**
114   * @serialData the key class, number of entries, first key, first value, second key, second value,
115   *     and so on.
116   */
117  @GwtIncompatible // java.io.ObjectOutputStream
118  private void writeObject(ObjectOutputStream stream) throws IOException {
119    stream.defaultWriteObject();
120    stream.writeObject(keyTypeOrObjectUnderJ2cl);
121    Serialization.writeMap(this, stream);
122  }
123
124  @SuppressWarnings("unchecked") // reading field populated by writeObject
125  @GwtIncompatible // java.io.ObjectInputStream
126  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
127    stream.defaultReadObject();
128    keyTypeOrObjectUnderJ2cl = (Class<K>) requireNonNull(stream.readObject());
129    /*
130     * TODO: cpovirk - Pre-size the HashMap based on the number of enum values? (But *not* based on
131     * the number of entries in the map, as that makes it easy for hostile inputs to trigger lots of
132     * allocation—not that any program should be deserializing hostile inputs to begin with!)
133     */
134    setDelegates(new EnumMap<K, V>(keyTypeOrObjectUnderJ2cl), new HashMap<V, K>());
135    Serialization.populateMap(this, stream);
136  }
137
138  @GwtIncompatible // only needed in emulated source.
139  private static final long serialVersionUID = 0;
140}