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