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Guava is a suite of core and expanded libraries that include utility classes, Google's collections, I/O classes, and much more. This project includes GWT-friendly sources.
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/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.EnumMap;
import java.util.Map;

/**
 * A {@code BiMap} backed by two {@code EnumMap} instances. Null keys and values are not permitted.
 * An {@code EnumBiMap} and its inverse are both serializable.
 *
 * See the Guava User Guide article on  {@code BiMap}.
 *
 * @author Mike Bostock
 * @since 2.0
 */
@GwtCompatible(emulated = true)
public final class EnumBiMap, V extends Enum> extends AbstractBiMap {
  private transient Class keyType;
  private transient Class valueType;

  /**
   * Returns a new, empty {@code EnumBiMap} using the specified key and value types.
   *
   * @param keyType the key type
   * @param valueType the value type
   */
  public static , V extends Enum> EnumBiMap create(
      Class keyType, Class valueType) {
    return new EnumBiMap<>(keyType, valueType);
  }

  /**
   * Returns a new bimap with the same mappings as the specified map. If the specified map is an
   * {@code EnumBiMap}, the new bimap has the same types as the provided map. Otherwise, the
   * specified map must contain at least one mapping, in order to determine the key and value types.
   *
   * @param map the map whose mappings are to be placed in this map
   * @throws IllegalArgumentException if map is not an {@code EnumBiMap} instance and contains no
   *     mappings
   */
  public static , V extends Enum> EnumBiMap create(Map map) {
    EnumBiMap bimap = create(inferKeyType(map), inferValueType(map));
    bimap.putAll(map);
    return bimap;
  }

  private EnumBiMap(Class keyType, Class valueType) {
    super(
        WellBehavedMap.wrap(new EnumMap(keyType)),
        WellBehavedMap.wrap(new EnumMap(valueType)));
    this.keyType = keyType;
    this.valueType = valueType;
  }

  static > Class inferKeyType(Map map) {
    if (map instanceof EnumBiMap) {
      return ((EnumBiMap) map).keyType();
    }
    if (map instanceof EnumHashBiMap) {
      return ((EnumHashBiMap) map).keyType();
    }
    checkArgument(!map.isEmpty());
    return map.keySet().iterator().next().getDeclaringClass();
  }

  private static > Class inferValueType(Map map) {
    if (map instanceof EnumBiMap) {
      return ((EnumBiMap) map).valueType;
    }
    checkArgument(!map.isEmpty());
    return map.values().iterator().next().getDeclaringClass();
  }

  /** Returns the associated key type. */
  public Class keyType() {
    return keyType;
  }

  /** Returns the associated value type. */
  public Class valueType() {
    return valueType;
  }

  @Override
  K checkKey(K key) {
    return checkNotNull(key);
  }

  @Override
  V checkValue(V value) {
    return checkNotNull(value);
  }

  /**
   * @serialData the key class, value class, number of entries, first key, first value, second key,
   *     second value, and so on.
   */
  @GwtIncompatible // java.io.ObjectOutputStream
  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    stream.writeObject(keyType);
    stream.writeObject(valueType);
    Serialization.writeMap(this, stream);
  }

  @SuppressWarnings("unchecked") // reading fields populated by writeObject
  @GwtIncompatible // java.io.ObjectInputStream
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    keyType = (Class) stream.readObject();
    valueType = (Class) stream.readObject();
    setDelegates(
        WellBehavedMap.wrap(new EnumMap(keyType)),
        WellBehavedMap.wrap(new EnumMap(valueType)));
    Serialization.populateMap(this, stream);
  }

  @GwtIncompatible // not needed in emulated source.
  private static final long serialVersionUID = 0;
}