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 * "http://code.google.com/p/guava-libraries/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  V put(R rowKey, C columnKey, V value);
144
145  /**
146   * Copies all mappings from the specified table to this table. The effect is
147   * equivalent to calling {@link #put} with each row key / column key / value
148   * mapping in {@code table}.
149   *
150   * @param table the table to add to this table
151   */
152  void putAll(Table<? extends R, ? extends C, ? extends V> table);
153
154  /**
155   * Removes the mapping, if any, associated with the given keys.
156   *
157   * @param rowKey row key of mapping to be removed
158   * @param columnKey column key of mapping to be removed
159   * @return the value previously associated with the keys, or {@code null} if
160   *     no such value existed
161   */
162  V remove(@Nullable Object rowKey, @Nullable Object columnKey);
163
164  // Views
165
166  /**
167   * Returns a view of all mappings that have the given row key. For each row
168   * key / column key / value mapping in the table with that row key, the
169   * returned map associates the column key with the value. If no mappings in
170   * the table have the provided row key, an empty map is returned.
171   *
172   * <p>Changes to the returned map will update the underlying table, and vice
173   * versa.
174   *
175   * @param rowKey key of row to search for in the table
176   * @return the corresponding map from column keys to values
177   */
178  Map<C, V> row(R rowKey);
179
180  /**
181   * Returns a view of all mappings that have the given column key. For each row
182   * key / column key / value mapping in the table with that column key, the
183   * returned map associates the row key with the value. If no mappings in the
184   * table have the provided column key, an empty map is returned.
185   *
186   * <p>Changes to the returned map will update the underlying table, and vice
187   * versa.
188   *
189   * @param columnKey key of column to search for in the table
190   * @return the corresponding map from row keys to values
191   */
192  Map<R, V> column(C columnKey);
193
194  /**
195   * Returns a set of all row key / column key / value triplets. Changes to the
196   * returned set will update the underlying table, and vice versa. The cell set
197   * does not support the {@code add} or {@code addAll} methods.
198   *
199   * @return set of table cells consisting of row key / column key / value
200   *     triplets
201   */
202  Set<Cell<R, C, V>> cellSet();
203
204  /**
205   * Returns a set of row keys that have one or more values in the table.
206   * Changes to the set will update the underlying table, and vice versa.
207   *
208   * @return set of row keys
209   */
210  Set<R> rowKeySet();
211
212  /**
213   * Returns a set of column keys that have one or more values in the table.
214   * Changes to the set will update the underlying table, and vice versa.
215   *
216   * @return set of column keys
217   */
218  Set<C> columnKeySet();
219
220  /**
221   * Returns a collection of all values, which may contain duplicates. Changes
222   * to the returned collection will update the underlying table, and vice
223   * versa.
224   *
225   * @return collection of values
226   */
227  Collection<V> values();
228
229  /**
230   * Returns a view that associates each row key with the corresponding map from
231   * column keys to values. Changes to the returned map will update this table.
232   * The returned map does not support {@code put()} or {@code putAll()}, or
233   * {@code setValue()} on its entries.
234   *
235   * <p>In contrast, the maps returned by {@code rowMap().get()} have the same
236   * behavior as those returned by {@link #row}. Those maps may support {@code
237   * setValue()}, {@code put()}, and {@code putAll()}.
238   *
239   * @return a map view from each row key to a secondary map from column keys to
240   *     values
241   */
242  Map<R, Map<C, V>> rowMap();
243
244  /**
245   * Returns a view that associates each column key with the corresponding map
246   * from row keys to values. Changes to the returned map will update this
247   * table. The returned map does not support {@code put()} or {@code putAll()},
248   * or {@code setValue()} on its entries.
249   *
250   * <p>In contrast, the maps returned by {@code columnMap().get()} have the
251   * same behavior as those returned by {@link #column}. Those maps may support
252   * {@code setValue()}, {@code put()}, and {@code putAll()}.
253   *
254   * @return a map view from each column key to a secondary map from row keys to
255   *     values
256   */
257  Map<C, Map<R, V>> columnMap();
258
259  /**
260   * Row key / column key / value triplet corresponding to a mapping in a table.
261   *
262   * @since 7.0
263   */
264  interface Cell<R, C, V> {
265    /**
266     * Returns the row key of this cell.
267     */
268    R getRowKey();
269
270    /**
271     * Returns the column key of this cell.
272     */
273    C getColumnKey();
274
275    /**
276     * Returns the value of this cell.
277     */
278    V getValue();
279
280    /**
281     * Compares the specified object with this cell for equality. Two cells are
282     * equal when they have equal row keys, column keys, and values.
283     */
284    @Override
285    boolean equals(@Nullable Object obj);
286
287    /**
288     * Returns the hash code of this cell.
289     *
290     * <p>The hash code of a table cell is equal to {@link
291     * Objects#hashCode}{@code (e.getRowKey(), e.getColumnKey(), e.getValue())}.
292     */
293    @Override
294    int hashCode();
295  }
296}