001/*
002 * Copyright (C) 2012 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.reflect;
016
017import com.google.errorprone.annotations.CanIgnoreReturnValue;
018import com.google.errorprone.annotations.DoNotMock;
019import java.util.Map;
020import javax.annotation.CheckForNull;
021
022/**
023 * A map, each entry of which maps a {@link TypeToken} to an instance of that type. In addition to
024 * implementing {@code Map}, the additional type-safe operations {@link #putInstance} and {@link
025 * #getInstance} are available.
026 *
027 * <p>Generally, implementations don't support {@link #put} and {@link #putAll} because there is no
028 * way to check an object at runtime to be an instance of a {@link TypeToken}. Instead, caller
029 * should use the type safe {@link #putInstance}.
030 *
031 * <p>Also, if caller suppresses unchecked warnings and passes in an {@code Iterable<String>} for
032 * type {@code Iterable<Integer>}, the map won't be able to detect and throw type error.
033 *
034 * <p>Like any other {@code Map<Class, Object>}, this map may contain entries for primitive types,
035 * and a primitive type and its corresponding wrapper type may map to different values.
036 *
037 * <p>This class's support for {@code null} requires some explanation. For details, see {@link
038 * com.google.common.collect.ClassToInstanceMap}. Its explanation applies equally well to {@code
039 * TypeToInstanceMap}.
040 *
041 * @param <B> the common supertype that all entries must share; often this is simply {@link Object}
042 * @author Ben Yu
043 * @since 13.0
044 */
045@DoNotMock("Use ImmutableTypeToInstanceMap or MutableTypeToInstanceMap")
046@ElementTypesAreNonnullByDefault
047public interface TypeToInstanceMap<B> extends Map<TypeToken<? extends B>, B> {
048
049  /**
050   * Returns the value the specified class is mapped to, or {@code null} if no entry for this class
051   * is present. This will only return a value that was bound to this specific class, not a value
052   * that may have been bound to a subtype.
053   *
054   * <p>{@code getInstance(Foo.class)} is equivalent to {@code
055   * getInstance(TypeToken.of(Foo.class))}.
056   */
057  @CheckForNull
058  <T extends B> T getInstance(Class<T> type);
059
060  /**
061   * Returns the value the specified type is mapped to, or {@code null} if no entry for this type is
062   * present. This will only return a value that was bound to this specific type, not a value that
063   * may have been bound to a subtype.
064   */
065  @CheckForNull
066  <T extends B> T getInstance(TypeToken<T> type);
067
068  /**
069   * Maps the specified class to the specified value. Does <i>not</i> associate this value with any
070   * of the class's supertypes.
071   *
072   * <p>{@code putInstance(Foo.class, foo)} is equivalent to {@code
073   * putInstance(TypeToken.of(Foo.class), foo)}.
074   *
075   * @return the value previously associated with this class (possibly {@code null}), or {@code
076   *     null} if there was no previous entry.
077   */
078  @CanIgnoreReturnValue
079  @CheckForNull
080  <T extends B> T putInstance(Class<T> type, T value);
081
082  /**
083   * Maps the specified type to the specified value. Does <i>not</i> associate this value with any
084   * of the type's supertypes.
085   *
086   * @return the value previously associated with this type (possibly {@code null}), or {@code null}
087   *     if there was no previous entry.
088   */
089  @CanIgnoreReturnValue
090  @CheckForNull
091  <T extends B> T putInstance(TypeToken<T> type, T value);
092}