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
017package com.google.common.collect;
018
019import com.google.common.primitives.Primitives;
020
021import 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 */
030public 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}