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

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Here is the source code for com.google.common.collect.MutableClassToInstanceMap.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 com.google.common.collect.MapConstraints.ConstrainedMap;
import com.google.common.primitives.Primitives;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

/**
 * A mutable class-to-instance map backed by an arbitrary user-provided map.
 * See also {@link ImmutableClassToInstanceMap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">
 * {@code ClassToInstanceMap}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@SuppressWarnings("serial") // using writeReplace instead of standard serialization
public final class MutableClassToInstanceMap<B> extends ConstrainedMap<Class<? extends B>, B>
        implements ClassToInstanceMap<B>, Serializable {

    /**
     * Returns a new {@code MutableClassToInstanceMap} instance backed by a {@link
     * HashMap} using the default initial capacity and load factor.
     */
    public static <B> MutableClassToInstanceMap<B> create() {
        return new MutableClassToInstanceMap<B>(new HashMap<Class<? extends B>, B>());
    }

    /**
     * Returns a new {@code MutableClassToInstanceMap} instance backed by a given
     * empty {@code backingMap}. The caller surrenders control of the backing map,
     * and thus should not allow any direct references to it to remain accessible.
     */
    public static <B> MutableClassToInstanceMap<B> create(Map<Class<? extends B>, B> backingMap) {
        return new MutableClassToInstanceMap<B>(backingMap);
    }

    private MutableClassToInstanceMap(Map<Class<? extends B>, B> delegate) {
        super(delegate, VALUE_CAN_BE_CAST_TO_KEY);
    }

    private static final MapConstraint<Class<?>, Object> VALUE_CAN_BE_CAST_TO_KEY = new MapConstraint<Class<?>, Object>() {
        @Override
        public void checkKeyValue(Class<?> key, Object value) {
            cast(key, value);
        }
    };

    @Override
    public <T extends B> T putInstance(Class<T> type, T value) {
        return cast(type, put(type, value));
    }

    @Override
    public <T extends B> T getInstance(Class<T> type) {
        return cast(type, get(type));
    }

    private static <B, T extends B> T cast(Class<T> type, B value) {
        return Primitives.wrap(type).cast(value);
    }

    private Object writeReplace() {
        return new SerializedForm(delegate());
    }

    /**
     * Serialized form of the map, to avoid serializing the constraint.
     */
    private static final class SerializedForm<B> implements Serializable {
        private final Map<Class<? extends B>, B> backingMap;

        SerializedForm(Map<Class<? extends B>, B> backingMap) {
            this.backingMap = backingMap;
        }

        Object readResolve() {
            return create(backingMap);
        }

        private static final long serialVersionUID = 0;
    }
}