001/* 002 * Copyright (C) 2012 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.reflect; 018 019import com.google.common.annotations.Beta; 020 021import java.util.Map; 022 023import javax.annotation.Nullable; 024 025/** 026 * A map, each entry of which maps a {@link TypeToken} to an instance of that type. 027 * In addition to implementing {@code Map}, the additional type-safe operations 028 * {@link #putInstance} and {@link #getInstance} are available. 029 * 030 * <p>Generally, implementations don't support {@link #put} and {@link #putAll} 031 * because there is no way to check an object at runtime to be an instance of a 032 * {@link TypeToken}. Instead, caller should use the type safe {@link #putInstance}. 033 * 034 * <p>Also, if caller suppresses unchecked warnings and passes in an {@code Iterable<String>} 035 * for type {@code Iterable<Integer>}, the map won't be able to detect and throw type error. 036 * 037 * <p>Like any other {@code Map<Class, Object>}, this map may contain entries 038 * for primitive types, and a primitive type and its corresponding wrapper type 039 * may map to different values. 040 * 041 * @param <B> the common supertype that all entries must share; often this is 042 * simply {@link Object} 043 * 044 * @author Ben Yu 045 * @since 13.0 046 */ 047@Beta 048public interface TypeToInstanceMap<B> extends Map<TypeToken<? extends B>, B> { 049 050 /** 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 * <p>{@code getInstance(Foo.class)} is equivalent to 057 * {@code getInstance(TypeToken.of(Foo.class))}. 058 */ 059 @Nullable 060 <T extends B> T getInstance(Class<T> type); 061 062 /** 063 * Maps the specified class to the specified value. Does <i>not</i> associate 064 * this value with any of the class's supertypes. 065 * 066 * <p>{@code putInstance(Foo.class, foo)} is equivalent to 067 * {@code putInstance(TypeToken.of(Foo.class), foo)}. 068 * 069 * @return the value previously associated with this class (possibly {@code null}), 070 * or {@code null} if there was no previous entry. 071 */ 072 @Nullable 073 <T extends B> T putInstance(Class<T> type, @Nullable T value); 074 075 /** 076 * Returns the value the specified type is mapped to, or {@code null} if no 077 * entry for this type is present. This will only return a value that was 078 * bound to this specific type, not a value that may have been bound to a subtype. 079 */ 080 @Nullable 081 <T extends B> T getInstance(TypeToken<T> type); 082 083 /** 084 * Maps the specified type to the specified value. Does <i>not</i> associate 085 * this value with any of the type's supertypes. 086 * 087 * @return the value previously associated with this type (possibly {@code null}), 088 * or {@code null} if there was no previous entry. 089 */ 090 @Nullable 091 <T extends B> T putInstance(TypeToken<T> type, @Nullable T value); 092}