    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.annotations.GwtCompatible;
    020
    021    import java.util.Map;
    022
    023    import javax.annotation.Nullable;
    024
    025    /**
    026     * A map, each entry of which maps a Java
    027     * <a href="http://tinyurl.com/2cmwkz">raw type</a> to an instance of that type.
    028     * In addition to implementing {@code Map}, the additional type-safe operations
    029     * {@link #putInstance} and {@link #getInstance} are available.
    030     *
    031     * <p>Like any other {@code Map<Class, Object>}, this map may contain entries
    032     * for primitive types, and a primitive type and its corresponding wrapper type
    033     * may map to different values.
    034     *
    035     * <p>See the Guava User Guide article on <a href=
    036     * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#ClassToInstanceMap">
    037     * {@code ClassToInstanceMap}</a>.
    038     *
    039     * <p>To map a generic type to an instance of that type, use {@link
    040     * com.google.common.reflect.TypeToInstanceMap} instead.
    041     *
    042     * @param <B> the common supertype that all entries must share; often this is
    043     *     simply {@link Object}
    044     *
    045     * @author Kevin Bourrillion
    046     * @since 2.0 (imported from Google Collections Library)
    047     */
    048    @GwtCompatible
    049    public interface ClassToInstanceMap<B> extends Map<Class<? extends B>, B> {
    050      /**
    051       * Returns the value the specified class is mapped to, or {@code null} if no
    052       * entry for this class is present. This will only return a value that was
    053       * bound to this specific class, not a value that may have been bound to a
    054       * subtype.
    055       */
    056      <T extends B> T getInstance(Class<T> type);
    057
    058      /**
    059       * Maps the specified class to the specified value. Does <i>not</i> associate
    060       * this value with any of the class's supertypes.
    061       *
    062       * @return the value previously associated with this class (possibly {@code
    063       *     null}), or {@code null} if there was no previous entry.
    064       */
    065      <T extends B> T putInstance(Class<T> type, @Nullable T value);
    066    }