    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     * @author Kevin Bourrillion
    030     * @since 2.0 (imported from Google Collections Library)
    031     */
    032    public final class MutableClassToInstanceMap<B>
    033        extends ConstrainedMap<Class<? extends B>, B>
    034        implements ClassToInstanceMap<B> {
    035
    036      /**
    037       * Returns a new {@code MutableClassToInstanceMap} instance backed by a {@link
    038       * HashMap} using the default initial capacity and load factor.
    039       */
    040      public static <B> MutableClassToInstanceMap<B> create() {
    041        return new MutableClassToInstanceMap<B>(
    042            new HashMap<Class<? extends B>, B>());
    043      }
    044
    045      /**
    046       * Returns a new {@code MutableClassToInstanceMap} instance backed by a given
    047       * empty {@code backingMap}. The caller surrenders control of the backing map,
    048       * and thus should not allow any direct references to it to remain accessible.
    049       */
    050      public static <B> MutableClassToInstanceMap<B> create(
    051          Map<Class<? extends B>, B> backingMap) {
    052        return new MutableClassToInstanceMap<B>(backingMap);
    053      }
    054
    055      private MutableClassToInstanceMap(Map<Class<? extends B>, B> delegate) {
    056        super(delegate, VALUE_CAN_BE_CAST_TO_KEY);
    057      }
    058
    059      private static final MapConstraint<Class<?>, Object> VALUE_CAN_BE_CAST_TO_KEY
    060          = new MapConstraint<Class<?>, Object>() {
    061        @Override
    062        public void checkKeyValue(Class<?> key, Object value) {
    063          cast(key, value);
    064        }
    065      };
    066
    067      @Override
    068      public <T extends B> T putInstance(Class<T> type, T value) {
    069        return cast(type, put(type, value));
    070      }
    071
    072      @Override
    073      public <T extends B> T getInstance(Class<T> type) {
    074        return cast(type, get(type));
    075      }
    076
    077      private static <B, T extends B> T cast(Class<T> type, B value) {
    078        return Primitives.wrap(type).cast(value);
    079      }
    080
    081      private static final long serialVersionUID = 0;
    082    }