001 /*
002 * Copyright (C) 2009 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.primitives.Primitives;
020
021 import java.util.Map;
022
023 /**
024 * A class-to-instance map backed by an {@link ImmutableMap}. See also {@link
025 * MutableClassToInstanceMap}.
026 *
027 * @author Kevin Bourrillion
028 * @since 2 (imported from Google Collections Library)
029 */
030 public final class ImmutableClassToInstanceMap<B> extends
031 ForwardingMap<Class<? extends B>, B> implements ClassToInstanceMap<B> {
032 /**
033 * Returns a new builder. The generated builder is equivalent to the builder
034 * created by the {@link Builder} constructor.
035 */
036 public static <B> Builder<B> builder() {
037 return new Builder<B>();
038 }
039
040 /**
041 * A builder for creating immutable class-to-instance maps. Example:
042 * <pre> {@code
043 *
044 * static final ImmutableClassToInstanceMap<Handler> HANDLERS =
045 * new ImmutableClassToInstanceMap.Builder<Handler>()
046 * .put(FooHandler.class, new FooHandler())
047 * .put(BarHandler.class, new SubBarHandler())
048 * .put(Handler.class, new QuuxHandler())
049 * .build();}</pre>
050 *
051 * After invoking {@link #build()} it is still possible to add more entries
052 * and build again. Thus each map generated by this builder will be a superset
053 * of any map generated before it.
054 *
055 * @since 2 (imported from Google Collections Library)
056 */
057 public static final class Builder<B> {
058 private final ImmutableMap.Builder<Class<? extends B>, B> mapBuilder
059 = ImmutableMap.builder();
060
061 /**
062 * Associates {@code key} with {@code value} in the built map. Duplicate
063 * keys are not allowed, and will cause {@link #build} to fail.
064 */
065 public <T extends B> Builder<B> put(Class<T> type, T value) {
066 mapBuilder.put(type, value);
067 return this;
068 }
069
070 /**
071 * Associates all of {@code map's} keys and values in the built map.
072 * Duplicate keys are not allowed, and will cause {@link #build} to fail.
073 *
074 * @throws NullPointerException if any key or value in {@code map} is null
075 * @throws ClassCastException if any value is not an instance of the type
076 * specified by its key
077 */
078 public <T extends B> Builder<B> putAll(
079 Map<? extends Class<? extends T>, ? extends T> map) {
080 for (Entry<? extends Class<? extends T>, ? extends T> entry
081 : map.entrySet()) {
082 Class<? extends T> type = entry.getKey();
083 T value = entry.getValue();
084 mapBuilder.put(type, cast(type, value));
085 }
086 return this;
087 }
088
089 private static <B, T extends B> T cast(Class<T> type, B value) {
090 return Primitives.wrap(type).cast(value);
091 }
092
093 /**
094 * Returns a new immutable class-to-instance map containing the entries
095 * provided to this builder.
096 *
097 * @throws IllegalArgumentException if duplicate keys were added
098 */
099 public ImmutableClassToInstanceMap<B> build() {
100 return new ImmutableClassToInstanceMap<B>(mapBuilder.build());
101 }
102 }
103
104 /**
105 * Returns an immutable map containing the same entries as {@code map}. If
106 * {@code map} somehow contains entries with duplicate keys (for example, if
107 * it is a {@code SortedMap} whose comparator is not <i>consistent with
108 * equals</i>), the results of this method are undefined.
109 *
110 * <p><b>Note:</b> Despite what the method name suggests, if {@code map} is
111 * an {@code ImmutableClassToInstanceMap}, no copy will actually be performed.
112 *
113 * @throws NullPointerException if any key or value in {@code map} is null
114 * @throws ClassCastException if any value is not an instance of the type
115 * specified by its key
116 */
117 public static <B, S extends B> ImmutableClassToInstanceMap<B> copyOf(
118 Map<? extends Class<? extends S>, ? extends S> map) {
119 if (map instanceof ImmutableClassToInstanceMap) {
120 @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
121 // Eclipse won't compile if we cast to the parameterized type.
122 ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap) map;
123 return cast;
124 }
125 return new Builder<B>().putAll(map).build();
126 }
127
128 private final ImmutableMap<Class<? extends B>, B> delegate;
129
130 private ImmutableClassToInstanceMap(
131 ImmutableMap<Class<? extends B>, B> delegate) {
132 this.delegate = delegate;
133 }
134
135 @Override protected Map<Class<? extends B>, B> delegate() {
136 return delegate;
137 }
138
139 @Override
140 @SuppressWarnings("unchecked") // value could not get in if not a T
141 public <T extends B> T getInstance(Class<T> type) {
142 return (T) delegate.get(type);
143 }
144
145 /**
146 * Guaranteed to throw an exception and leave the map unmodified.
147 *
148 * @throws UnsupportedOperationException always
149 */
150 @Override
151 public <T extends B> T putInstance(Class<T> type, T value) {
152 throw new UnsupportedOperationException();
153 }
154 }