com.google.common.collect.EnumHashBiMap.java Source code

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Here is the source code for com.google.common.collect.EnumHashBiMap.java

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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.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.HashMap;
import java.util.Map;

import javax.annotation.Nullable;

/**
 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
 * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
 * but null values are. An {@code EnumHashBiMap} and its inverse are both
 * serializable.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">
 * {@code BiMap}</a>.
 *
 * @author Mike Bostock
 * @since 2.0
 */
@GwtCompatible(emulated = true)
public final class EnumHashBiMap<K extends Enum<K>, V> extends AbstractBiMap<K, V> {
    private transient Class<K> keyType;

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

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

    private EnumHashBiMap(Class<K> keyType) {
        super(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
                Maps.<V, K>newHashMapWithExpectedSize(keyType.getEnumConstants().length));
        this.keyType = keyType;
    }

    // Overriding these 3 methods to show that values may be null (but not keys)

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

    @Override
    public V put(K key, @Nullable V value) {
        return super.put(key, value);
    }

    @Override
    public V forcePut(K key, @Nullable V value) {
        return super.forcePut(key, value);
    }

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

    /**
     * @serialData the key 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);
        Serialization.writeMap(this, stream);
    }

    @SuppressWarnings("unchecked") // reading field populated by writeObject
    @GwtIncompatible("java.io.ObjectInputStream")
    private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
        stream.defaultReadObject();
        keyType = (Class<K>) stream.readObject();
        setDelegates(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
                new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
        Serialization.populateMap(this, stream);
    }

    @GwtIncompatible("only needed in emulated source.")
    private static final long serialVersionUID = 0;
}