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
017package com.google.common.collect;
018
019import com.google.common.collect.MapConstraints.ConstrainedMap;
020import com.google.common.primitives.Primitives;
021
022import java.util.HashMap;
023import 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 */
036public 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}