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 (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    }