    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 2.0 (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 2.0 (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> key, T value) {
    066          mapBuilder.put(key, 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    }