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    }