    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
    017    package com.google.common.collect;
    018
    019    import com.google.common.collect.MapConstraints.ConstrainedMap;
    020    import com.google.common.primitives.Primitives;
    021
    022    import java.util.HashMap;
    023    import java.util.Map;
    024
    025    /**
    026     * A mutable class-to-instance map backed by an arbitrary user-provided map.
    027     * See also {@link ImmutableClassToInstanceMap}.
    028     *
    029     * <p>See the Guava User Guide article on <a href=
    030     * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#ClassToInstanceMap">
    031     * {@code ClassToInstanceMap}</a>.
    032     *
    033     * @author Kevin Bourrillion
    034     * @since 2.0 (imported from Google Collections Library)
    035     */
    036    public final class MutableClassToInstanceMap<B>
    037        extends ConstrainedMap<Class<? extends B>, B>
    038        implements ClassToInstanceMap<B> {
    039
    040      /**
    041       * Returns a new {@code MutableClassToInstanceMap} instance backed by a {@link
    042       * HashMap} using the default initial capacity and load factor.
    043       */
    044      public static <B> MutableClassToInstanceMap<B> create() {
    045        return new MutableClassToInstanceMap<B>(
    046            new HashMap<Class<? extends B>, B>());
    047      }
    048
    049      /**
    050       * Returns a new {@code MutableClassToInstanceMap} instance backed by a given
    051       * empty {@code backingMap}. The caller surrenders control of the backing map,
    052       * and thus should not allow any direct references to it to remain accessible.
    053       */
    054      public static <B> MutableClassToInstanceMap<B> create(
    055          Map<Class<? extends B>, B> backingMap) {
    056        return new MutableClassToInstanceMap<B>(backingMap);
    057      }
    058
    059      private MutableClassToInstanceMap(Map<Class<? extends B>, B> delegate) {
    060        super(delegate, VALUE_CAN_BE_CAST_TO_KEY);
    061      }
    062
    063      private static final MapConstraint<Class<?>, Object> VALUE_CAN_BE_CAST_TO_KEY
    064          = new MapConstraint<Class<?>, Object>() {
    065        @Override
    066        public void checkKeyValue(Class<?> key, Object value) {
    067          cast(key, value);
    068        }
    069      };
    070
    071      @Override
    072      public <T extends B> T putInstance(Class<T> type, T value) {
    073        return cast(type, put(type, value));
    074      }
    075
    076      @Override
    077      public <T extends B> T getInstance(Class<T> type) {
    078        return cast(type, get(type));
    079      }
    080
    081      private static <B, T extends B> T cast(Class<T> type, B value) {
    082        return Primitives.wrap(type).cast(value);
    083      }
    084
    085      private static final long serialVersionUID = 0;
    086    }