    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
    022    import java.util.Comparator;
    023    import java.util.Iterator;
    024    import java.util.NoSuchElementException;
    025    import java.util.SortedMap;
    026
    027    import javax.annotation.Nullable;
    028
    029    /**
    030     * A sorted map which forwards all its method calls to another sorted map.
    031     * Subclasses should override one or more methods to modify the behavior of
    032     * the backing sorted map as desired per the <a
    033     * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
    034     *
    035     * <p><i>Warning:</i> The methods of {@code ForwardingSortedMap} forward
    036     * <i>indiscriminately</i> to the methods of the delegate. For example,
    037     * overriding {@link #put} alone <i>will not</i> change the behavior of {@link
    038     * #putAll}, which can lead to unexpected behavior. In this case, you should
    039     * override {@code putAll} as well, either providing your own implementation, or
    040     * delegating to the provided {@code standardPutAll} method.
    041     *
    042     * <p>Each of the {@code standard} methods, where appropriate, use the
    043     * comparator of the map to test equality for both keys and values, unlike
    044     * {@code ForwardingMap}.
    045     *
    046     * <p>The {@code standard} methods and the collection views they return are not
    047     * guaranteed to be thread-safe, even when all of the methods that they depend
    048     * on are thread-safe.
    049     *
    050     * @author Mike Bostock
    051     * @author Louis Wasserman
    052     * @since 2.0 (imported from Google Collections Library)
    053     */
    054    @GwtCompatible
    055    public abstract class ForwardingSortedMap<K, V> extends ForwardingMap<K, V>
    056        implements SortedMap<K, V> {
    057      // TODO(user): identify places where thread safety is actually lost
    058
    059      /** Constructor for use by subclasses. */
    060      protected ForwardingSortedMap() {}
    061
    062      @Override protected abstract SortedMap<K, V> delegate();
    063
    064      @Override
    065      public Comparator<? super K> comparator() {
    066        return delegate().comparator();
    067      }
    068
    069      @Override
    070      public K firstKey() {
    071        return delegate().firstKey();
    072      }
    073
    074      @Override
    075      public SortedMap<K, V> headMap(K toKey) {
    076        return delegate().headMap(toKey);
    077      }
    078
    079      @Override
    080      public K lastKey() {
    081        return delegate().lastKey();
    082      }
    083
    084      @Override
    085      public SortedMap<K, V> subMap(K fromKey, K toKey) {
    086        return delegate().subMap(fromKey, toKey);
    087      }
    088
    089      @Override
    090      public SortedMap<K, V> tailMap(K fromKey) {
    091        return delegate().tailMap(fromKey);
    092      }
    093
    094      // unsafe, but worst case is a CCE is thrown, which callers will be expecting
    095      @SuppressWarnings("unchecked")
    096      private int unsafeCompare(Object k1, Object k2) {
    097        Comparator<? super K> comparator = comparator();
    098        if (comparator == null) {
    099          return ((Comparable<Object>) k1).compareTo(k2);
    100        } else {
    101          return ((Comparator<Object>) comparator).compare(k1, k2);
    102        }
    103      }
    104
    105      /**
    106       * A sensible definition of {@link #containsKey} in terms of the {@code
    107       * firstKey()} method of {@link #tailMap}. If you override {@link #tailMap},
    108       * you may wish to override {@link #containsKey} to forward to this
    109       * implementation.
    110       *
    111       * @since 7.0
    112       */
    113      @Override @Beta protected boolean standardContainsKey(@Nullable Object key) {
    114        try {
    115          // any CCE will be caught
    116          @SuppressWarnings("unchecked")
    117          SortedMap<Object, V> self = (SortedMap<Object, V>) this;
    118          Object ceilingKey = self.tailMap(key).firstKey();
    119          return unsafeCompare(ceilingKey, key) == 0;
    120        } catch (ClassCastException e) {
    121          return false;
    122        } catch (NoSuchElementException e) {
    123          return false;
    124        } catch (NullPointerException e) {
    125          return false;
    126        }
    127      }
    128
    129      /**
    130       * A sensible definition of {@link #remove} in terms of the {@code
    131       * iterator()} of the {@code entrySet()} of {@link #tailMap}. If you override
    132       * {@link #tailMap}, you may wish to override {@link #remove} to forward
    133       * to this implementation.
    134       *
    135       * @since 7.0
    136       */
    137      @Override @Beta protected V standardRemove(@Nullable Object key) {
    138        try {
    139          // any CCE will be caught
    140          @SuppressWarnings("unchecked")
    141          SortedMap<Object, V> self = (SortedMap<Object, V>) this;
    142          Iterator<Entry<Object, V>> entryIterator =
    143              self.tailMap(key).entrySet().iterator();
    144          if (entryIterator.hasNext()) {
    145            Entry<Object, V> ceilingEntry = entryIterator.next();
    146            if (unsafeCompare(ceilingEntry.getKey(), key) == 0) {
    147              V value = ceilingEntry.getValue();
    148              entryIterator.remove();
    149              return value;
    150            }
    151          }
    152        } catch (ClassCastException e) {
    153          return null;
    154        } catch (NullPointerException e) {
    155          return null;
    156        }
    157        return null;
    158      }
    159
    160      /**
    161       * A sensible default implementation of {@link #subMap(Object, Object)} in
    162       * terms of {@link #headMap(Object)} and {@link #tailMap(Object)}. In some
    163       * situations, you may wish to override {@link #subMap(Object, Object)} to
    164       * forward to this implementation.
    165       *
    166       * @since 7.0
    167       */
    168      @Beta protected SortedMap<K, V> standardSubMap(K fromKey, K toKey) {
    169        return tailMap(fromKey).headMap(toKey);
    170      }
    171    }