001/*
002 * Copyright (C) 2008 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.annotations.GwtCompatible;
020import com.google.common.base.Objects;
021
022import java.util.Collection;
023import java.util.Map;
024import java.util.Set;
025
026import javax.annotation.Nullable;
027
028/**
029 * A collection that associates an ordered pair of keys, called a row key and a
030 * column key, with a single value. A table may be sparse, with only a small
031 * fraction of row key / column key pairs possessing a corresponding value.
032 *
033 * <p>The mappings corresponding to a given row key may be viewed as a {@link
034 * Map} whose keys are the columns. The reverse is also available, associating a
035 * column with a row key / value map. Note that, in some implementations, data
036 * access by column key may have fewer supported operations or worse performance
037 * than data access by row key.
038 *
039 * <p>The methods returning collections or maps always return views of the
040 * underlying table. Updating the table can change the contents of those
041 * collections, and updating the collections will change the table.
042 *
043 * <p>All methods that modify the table are optional, and the views returned by
044 * the table may or may not be modifiable. When modification isn't supported,
045 * those methods will throw an {@link UnsupportedOperationException}.
046 *
047 * <p>See the Guava User Guide article on <a href=
048 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#table">
049 * {@code Table}</a>.
050 *
051 * @author Jared Levy
052 * @param <R> the type of the table row keys
053 * @param <C> the type of the table column keys
054 * @param <V> the type of the mapped values
055 * @since 7.0
056 */
057@GwtCompatible
058public interface Table<R, C, V> {
059  // TODO(jlevy): Consider adding methods similar to ConcurrentMap methods.
060
061  // Accessors
062
063  /**
064   * Returns {@code true} if the table contains a mapping with the specified
065   * row and column keys.
066   *
067   * @param rowKey key of row to search for
068   * @param columnKey key of column to search for
069   */
070  boolean contains(@Nullable Object rowKey, @Nullable Object columnKey);
071
072  /**
073   * Returns {@code true} if the table contains a mapping with the specified
074   * row key.
075   *
076   * @param rowKey key of row to search for
077   */
078  boolean containsRow(@Nullable Object rowKey);
079
080  /**
081   * Returns {@code true} if the table contains a mapping with the specified
082   * column.
083   *
084   * @param columnKey key of column to search for
085   */
086  boolean containsColumn(@Nullable Object columnKey);
087
088  /**
089   * Returns {@code true} if the table contains a mapping with the specified
090   * value.
091   *
092   * @param value value to search for
093   */
094  boolean containsValue(@Nullable Object value);
095
096  /**
097   * Returns the value corresponding to the given row and column keys, or
098   * {@code null} if no such mapping exists.
099   *
100   * @param rowKey key of row to search for
101   * @param columnKey key of column to search for
102   */
103  V get(@Nullable Object rowKey, @Nullable Object columnKey);
104
105  /** Returns {@code true} if the table contains no mappings. */
106  boolean isEmpty();
107
108  /**
109   * Returns the number of row key / column key / value mappings in the table.
110   */
111  int size();
112
113  /**
114   * Compares the specified object with this table for equality. Two tables are
115   * equal when their cell views, as returned by {@link #cellSet}, are equal.
116   */
117  @Override
118  boolean equals(@Nullable Object obj);
119
120  /**
121   * Returns the hash code for this table. The hash code of a table is defined
122   * as the hash code of its cell view, as returned by {@link #cellSet}.
123   */
124  @Override
125  int hashCode();
126
127  // Mutators
128
129  /** Removes all mappings from the table. */
130  void clear();
131
132  /**
133   * Associates the specified value with the specified keys. If the table
134   * already contained a mapping for those keys, the old value is replaced with
135   * the specified value.
136   *
137   * @param rowKey row key that the value should be associated with
138   * @param columnKey column key that the value should be associated with
139   * @param value value to be associated with the specified keys
140   * @return the value previously associated with the keys, or {@code null} if
141   *     no mapping existed for the keys
142   */
143  @Nullable
144  V put(R rowKey, C columnKey, V value);
145
146  /**
147   * Copies all mappings from the specified table to this table. The effect is
148   * equivalent to calling {@link #put} with each row key / column key / value
149   * mapping in {@code table}.
150   *
151   * @param table the table to add to this table
152   */
153  void putAll(Table<? extends R, ? extends C, ? extends V> table);
154
155  /**
156   * Removes the mapping, if any, associated with the given keys.
157   *
158   * @param rowKey row key of mapping to be removed
159   * @param columnKey column key of mapping to be removed
160   * @return the value previously associated with the keys, or {@code null} if
161   *     no such value existed
162   */
163  @Nullable
164  V remove(@Nullable Object rowKey, @Nullable Object columnKey);
165
166  // Views
167
168  /**
169   * Returns a view of all mappings that have the given row key. For each row
170   * key / column key / value mapping in the table with that row key, the
171   * returned map associates the column key with the value. If no mappings in
172   * the table have the provided row key, an empty map is returned.
173   *
174   * <p>Changes to the returned map will update the underlying table, and vice
175   * versa.
176   *
177   * @param rowKey key of row to search for in the table
178   * @return the corresponding map from column keys to values
179   */
180  Map<C, V> row(R rowKey);
181
182  /**
183   * Returns a view of all mappings that have the given column key. For each row
184   * key / column key / value mapping in the table with that column key, the
185   * returned map associates the row key with the value. If no mappings in the
186   * table have the provided column key, an empty map is returned.
187   *
188   * <p>Changes to the returned map will update the underlying table, and vice
189   * versa.
190   *
191   * @param columnKey key of column to search for in the table
192   * @return the corresponding map from row keys to values
193   */
194  Map<R, V> column(C columnKey);
195
196  /**
197   * Returns a set of all row key / column key / value triplets. Changes to the
198   * returned set will update the underlying table, and vice versa. The cell set
199   * does not support the {@code add} or {@code addAll} methods.
200   *
201   * @return set of table cells consisting of row key / column key / value
202   *     triplets
203   */
204  Set<Cell<R, C, V>> cellSet();
205
206  /**
207   * Returns a set of row keys that have one or more values in the table.
208   * Changes to the set will update the underlying table, and vice versa.
209   *
210   * @return set of row keys
211   */
212  Set<R> rowKeySet();
213
214  /**
215   * Returns a set of column keys that have one or more values in the table.
216   * Changes to the set will update the underlying table, and vice versa.
217   *
218   * @return set of column keys
219   */
220  Set<C> columnKeySet();
221
222  /**
223   * Returns a collection of all values, which may contain duplicates. Changes
224   * to the returned collection will update the underlying table, and vice
225   * versa.
226   *
227   * @return collection of values
228   */
229  Collection<V> values();
230
231  /**
232   * Returns a view that associates each row key with the corresponding map from
233   * column keys to values. Changes to the returned map will update this table.
234   * The returned map does not support {@code put()} or {@code putAll()}, or
235   * {@code setValue()} on its entries.
236   *
237   * <p>In contrast, the maps returned by {@code rowMap().get()} have the same
238   * behavior as those returned by {@link #row}. Those maps may support {@code
239   * setValue()}, {@code put()}, and {@code putAll()}.
240   *
241   * @return a map view from each row key to a secondary map from column keys to
242   *     values
243   */
244  Map<R, Map<C, V>> rowMap();
245
246  /**
247   * Returns a view that associates each column key with the corresponding map
248   * from row keys to values. Changes to the returned map will update this
249   * table. The returned map does not support {@code put()} or {@code putAll()},
250   * or {@code setValue()} on its entries.
251   *
252   * <p>In contrast, the maps returned by {@code columnMap().get()} have the
253   * same behavior as those returned by {@link #column}. Those maps may support
254   * {@code setValue()}, {@code put()}, and {@code putAll()}.
255   *
256   * @return a map view from each column key to a secondary map from row keys to
257   *     values
258   */
259  Map<C, Map<R, V>> columnMap();
260
261  /**
262   * Row key / column key / value triplet corresponding to a mapping in a table.
263   *
264   * @since 7.0
265   */
266  interface Cell<R, C, V> {
267    /**
268     * Returns the row key of this cell.
269     */
270    @Nullable
271    R getRowKey();
272
273    /**
274     * Returns the column key of this cell.
275     */
276    @Nullable
277    C getColumnKey();
278
279    /**
280     * Returns the value of this cell.
281     */
282    @Nullable
283    V getValue();
284
285    /**
286     * Compares the specified object with this cell for equality. Two cells are
287     * equal when they have equal row keys, column keys, and values.
288     */
289    @Override
290    boolean equals(@Nullable Object obj);
291
292    /**
293     * Returns the hash code of this cell.
294     *
295     * <p>The hash code of a table cell is equal to {@link
296     * Objects#hashCode}{@code (e.getRowKey(), e.getColumnKey(), e.getValue())}.
297     */
298    @Override
299    int hashCode();
300  }
301}