    001    /*
    002     * Copyright (C) 2007 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.annotations.Beta;
    020    import com.google.common.annotations.GwtCompatible;
    021    import com.google.common.base.Objects;
    022    import com.google.common.base.Supplier;
    023
    024    import java.util.Collection;
    025    import java.util.Iterator;
    026    import java.util.Map;
    027    import java.util.Set;
    028
    029    import javax.annotation.Nullable;
    030
    031    /**
    032     * A map which forwards all its method calls to another map. Subclasses should
    033     * override one or more methods to modify the behavior of the backing map as
    034     * desired per the <a
    035     * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
    036     *
    037     * <p><i>Warning:</i> The methods of {@code ForwardingMap} forward
    038     * <i>indiscriminately</i> to the methods of the delegate. For example,
    039     * overriding {@link #put} alone <i>will not</i> change the behavior of {@link
    040     * #putAll}, which can lead to unexpected behavior. In this case, you should
    041     * override {@code putAll} as well, either providing your own implementation, or
    042     * delegating to the provided {@code standardPutAll} method.
    043     *
    044     * <p>Each of the {@code standard} methods, where appropriate, use {@link
    045     * Objects#equal} to test equality for both keys and values. This may not be
    046     * the desired behavior for map implementations that use non-standard notions of
    047     * key equality, such as a {@code SortedMap} whose comparator is not consistent
    048     * with {@code equals}.
    049     *
    050     * <p>The {@code standard} methods and the collection views they return are not
    051     * guaranteed to be thread-safe, even when all of the methods that they depend
    052     * on are thread-safe.
    053     *
    054     * @author Kevin Bourrillion
    055     * @author Jared Levy
    056     * @author Louis Wasserman
    057     * @since 2.0 (imported from Google Collections Library)
    058     */
    059    @GwtCompatible
    060    public abstract class ForwardingMap<K, V> extends ForwardingObject
    061        implements Map<K, V> {
    062      // TODO(user): identify places where thread safety is actually lost
    063
    064      /** Constructor for use by subclasses. */
    065      protected ForwardingMap() {}
    066
    067      @Override protected abstract Map<K, V> delegate();
    068
    069      @Override
    070      public int size() {
    071        return delegate().size();
    072      }
    073
    074      @Override
    075      public boolean isEmpty() {
    076        return delegate().isEmpty();
    077      }
    078
    079      @Override
    080      public V remove(Object object) {
    081        return delegate().remove(object);
    082      }
    083
    084      @Override
    085      public void clear() {
    086        delegate().clear();
    087      }
    088
    089      @Override
    090      public boolean containsKey(Object key) {
    091        return delegate().containsKey(key);
    092      }
    093
    094      @Override
    095      public boolean containsValue(Object value) {
    096        return delegate().containsValue(value);
    097      }
    098
    099      @Override
    100      public V get(Object key) {
    101        return delegate().get(key);
    102      }
    103
    104      @Override
    105      public V put(K key, V value) {
    106        return delegate().put(key, value);
    107      }
    108
    109      @Override
    110      public void putAll(Map<? extends K, ? extends V> map) {
    111        delegate().putAll(map);
    112      }
    113
    114      @Override
    115      public Set<K> keySet() {
    116        return delegate().keySet();
    117      }
    118
    119      @Override
    120      public Collection<V> values() {
    121        return delegate().values();
    122      }
    123
    124      @Override
    125      public Set<Entry<K, V>> entrySet() {
    126        return delegate().entrySet();
    127      }
    128
    129      @Override public boolean equals(@Nullable Object object) {
    130        return object == this || delegate().equals(object);
    131      }
    132
    133      @Override public int hashCode() {
    134        return delegate().hashCode();
    135      }
    136
    137      /**
    138       * A sensible definition of {@link #putAll(Map)} in terms of {@link
    139       * #put(Object, Object)}. If you override {@link #put(Object, Object)}, you
    140       * may wish to override {@link #putAll(Map)} to forward to this
    141       * implementation.
    142       *
    143       * @since 7.0
    144       */
    145      @Beta protected void standardPutAll(Map<? extends K, ? extends V> map) {
    146        Maps.putAllImpl(this, map);
    147      }
    148
    149      /**
    150       * A sensible, albeit inefficient, definition of {@link #remove} in terms of
    151       * the {@code iterator} method of {@link #entrySet}. If you override {@link
    152       * #entrySet}, you may wish to override {@link #remove} to forward to this
    153       * implementation.
    154       *
    155       * <p>Alternately, you may wish to override {@link #remove} with {@code
    156       * keySet().remove}, assuming that approach would not lead to an infinite
    157       * loop.
    158       *
    159       * @since 7.0
    160       */
    161      @Beta protected V standardRemove(@Nullable Object key) {
    162        Iterator<Entry<K, V>> entryIterator = entrySet().iterator();
    163        while (entryIterator.hasNext()) {
    164          Entry<K, V> entry = entryIterator.next();
    165          if (Objects.equal(entry.getKey(), key)) {
    166            V value = entry.getValue();
    167            entryIterator.remove();
    168            return value;
    169          }
    170        }
    171        return null;
    172      }
    173
    174      /**
    175       * A sensible definition of {@link #clear} in terms of the {@code iterator}
    176       * method of {@link #entrySet}. In many cases, you may wish to override
    177       * {@link #clear} to forward to this implementation.
    178       *
    179       * @since 7.0
    180       */
    181      @Beta protected void standardClear() {
    182        Iterator<Entry<K, V>> entryIterator = entrySet().iterator();
    183        while (entryIterator.hasNext()) {
    184          entryIterator.next();
    185          entryIterator.remove();
    186        }
    187      }
    188
    189      /**
    190       * A sensible definition of {@link #keySet} in terms of the following methods:
    191       * {@link #clear}, {@link #containsKey}, {@link #isEmpty}, {@link #remove},
    192       * {@link #size}, and the {@code iterator} method of {@link #entrySet}. In
    193       * many cases, you may wish to override {@link #keySet} to forward to this
    194       * implementation.
    195       *
    196       * @since 7.0
    197       * @deprecated Use the {@code StandardKeySet} constructor instead.  This
    198       *             method will be removed from Guava in Guava release 11.0.
    199       */
    200      @Beta @Deprecated protected Set<K> standardKeySet() {
    201        return new StandardKeySet();
    202      }
    203
    204      /**
    205       * A sensible implementation of {@link Map#keySet} in terms of the following
    206       * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsKey},
    207       * {@link ForwardingMap#isEmpty}, {@link ForwardingMap#remove}, {@link
    208       * ForwardingMap#size}, and the {@link Set#iterator} method of {@link
    209       * ForwardingMap#entrySet}. In many cases, you may wish to override {@link
    210       * ForwardingMap#keySet} to forward to this implementation or a subclass
    211       * thereof.
    212       *
    213       * @since 10.0
    214       */
    215      @Beta
    216      protected class StandardKeySet extends Maps.KeySet<K, V> {
    217        public StandardKeySet() {}
    218
    219        @Override
    220        Map<K, V> map() {
    221          return ForwardingMap.this;
    222        }
    223      }
    224
    225      /**
    226       * A sensible, albeit inefficient, definition of {@link #containsKey} in terms
    227       * of the {@code iterator} method of {@link #entrySet}. If you override {@link
    228       * #entrySet}, you may wish to override {@link #containsKey} to forward to
    229       * this implementation.
    230       *
    231       * @since 7.0
    232       */
    233      @Beta protected boolean standardContainsKey(@Nullable Object key) {
    234        return Maps.containsKeyImpl(this, key);
    235      }
    236
    237      /**
    238       * A sensible definition of {@link #values} in terms of the following methods:
    239       * {@link #clear}, {@link #containsValue}, {@link #isEmpty}, {@link #size},
    240       * and the {@code iterator} method of {@link #entrySet}. In many cases, you
    241       * may wish to override {@link #values} to forward to this implementation.
    242       *
    243       * @since 7.0
    244       * @deprecated Use the {@code StandardValues} constructor instead.  This
    245       *             method will be removed from Guava in Guava release 11.0.
    246       */
    247      @Beta @Deprecated protected Collection<V> standardValues() {
    248        return new StandardValues();
    249      }
    250
    251      /**
    252       * A sensible implementation of {@link Map#values} in terms of the following
    253       * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsValue},
    254       * {@link ForwardingMap#isEmpty}, {@link ForwardingMap#size}, and the {@link
    255       * Set#iterator} method of {@link ForwardingMap#entrySet}. In many cases, you
    256       * may wish to override {@link ForwardingMap#values} to forward to this
    257       * implementation or a subclass thereof.
    258       *
    259       * @since 10.0
    260       */
    261      @Beta
    262      protected class StandardValues extends Maps.Values<K, V> {
    263        public StandardValues() {}
    264
    265        @Override
    266        Map<K, V> map() {
    267          return ForwardingMap.this;
    268        }
    269      }
    270
    271      /**
    272       * A sensible definition of {@link #containsValue} in terms of the {@code
    273       * iterator} method of {@link #entrySet}. If you override {@link #entrySet},
    274       * you may wish to override {@link #containsValue} to forward to this
    275       * implementation.
    276       *
    277       * @since 7.0
    278       */
    279      @Beta protected boolean standardContainsValue(@Nullable Object value) {
    280        return Maps.containsValueImpl(this, value);
    281      }
    282
    283      /**
    284       * A sensible definition of {@link #entrySet} in terms of the specified {@code
    285       * Supplier}, which is used to generate iterators over the entry set, and in
    286       * terms of the following methods: {@link #clear}, {@link #containsKey},
    287       * {@link #get}, {@link #isEmpty}, {@link #remove}, and {@link #size}. In many
    288       * cases, you may wish to override {@link #entrySet} to forward to this
    289       * implementation.
    290       *
    291       * @param entryIteratorSupplier A creator for iterators over the entry set.
    292       *        Each call to {@code get} must return an iterator that will
    293       *        traverse the entire entry set.
    294       *
    295       * @since 7.0
    296       * @deprecated Use {@code StandardEntrySet} instead.  This method will be
    297       *             removed from Guava in Guava release 11.0.
    298       */
    299      @Deprecated @Beta
    300       protected Set<Entry<K, V>> standardEntrySet(
    301          final Supplier<Iterator<Entry<K, V>>> entryIteratorSupplier) {
    302        return new StandardEntrySet() {
    303          @Override public Iterator<Map.Entry<K, V>> iterator() {
    304            return entryIteratorSupplier.get();
    305          }
    306        };
    307      }
    308
    309      /**
    310       * A sensible implementation of {@link Map#entrySet} in terms of the following
    311       * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsKey},
    312       * {@link ForwardingMap#get}, {@link ForwardingMap#isEmpty}, {@link
    313       * ForwardingMap#remove}, and {@link ForwardingMap#size}. In many cases, you
    314       * may wish to override {@link #entrySet} to forward to this implementation
    315       * or a subclass thereof.
    316       *
    317       * @since 10.0
    318       */
    319      @Beta
    320      protected abstract class StandardEntrySet extends Maps.EntrySet<K, V> {
    321        public StandardEntrySet() {}
    322
    323        @Override
    324        Map<K, V> map() {
    325          return ForwardingMap.this;
    326        }
    327      }
    328
    329      /**
    330       * A sensible definition of {@link #isEmpty} in terms of the {@code iterator}
    331       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
    332       * wish to override {@link #isEmpty} to forward to this implementation.
    333       *
    334       * @since 7.0
    335       */
    336      @Beta protected boolean standardIsEmpty() {
    337        return !entrySet().iterator().hasNext();
    338      }
    339
    340      /**
    341       * A sensible definition of {@link #equals} in terms of the {@code equals}
    342       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
    343       * wish to override {@link #equals} to forward to this implementation.
    344       *
    345       * @since 7.0
    346       */
    347      @Beta protected boolean standardEquals(@Nullable Object object) {
    348        return Maps.equalsImpl(this, object);
    349      }
    350
    351      /**
    352       * A sensible definition of {@link #hashCode} in terms of the {@code iterator}
    353       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
    354       * wish to override {@link #hashCode} to forward to this implementation.
    355       *
    356       * @since 7.0
    357       */
    358      @Beta protected int standardHashCode() {
    359        return Sets.hashCodeImpl(entrySet());
    360      }
    361
    362      /**
    363       * A sensible definition of {@link #toString} in terms of the {@code iterator}
    364       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
    365       * wish to override {@link #toString} to forward to this implementation.
    366       *
    367       * @since 7.0
    368       */
    369      @Beta protected String standardToString() {
    370        return Maps.toStringImpl(this);
    371      }
    372    }