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

Introduction

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

Source

/*
 * 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.
 *
 * <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 EnumBiMap<K extends Enum<K>, V extends Enum<V>> extends AbstractBiMap<K, V> {
    private transient Class<K> keyType;
    private transient Class<V> 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 <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V> create(Class<K> keyType,
            Class<V> valueType) {
        return new EnumBiMap<K, V>(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 <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V> create(Map<K, V> map) {
        EnumBiMap<K, V> bimap = create(inferKeyType(map), inferValueType(map));
        bimap.putAll(map);
        return bimap;
    }

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

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

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

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

    /** Returns the associated value type. */
    public Class<V> 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<K>) stream.readObject();
        valueType = (Class<V>) stream.readObject();
        setDelegates(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
                WellBehavedMap.wrap(new EnumMap<V, K>(valueType)));
        Serialization.populateMap(this, stream);
    }

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