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 static com.google.common.base.Preconditions.checkArgument; 020import static com.google.common.base.Preconditions.checkNotNull; 021import static java.util.Objects.requireNonNull; 022 023import com.google.common.annotations.GwtCompatible; 024import com.google.common.base.Supplier; 025import java.io.Serializable; 026import java.util.Comparator; 027import java.util.Iterator; 028import java.util.Map; 029import java.util.NoSuchElementException; 030import java.util.Set; 031import java.util.SortedMap; 032import java.util.SortedSet; 033import java.util.TreeMap; 034import javax.annotation.CheckForNull; 035 036/** 037 * Implementation of {@code Table} whose row keys and column keys are ordered by their natural 038 * ordering or by supplied comparators. When constructing a {@code TreeBasedTable}, you may provide 039 * comparators for the row keys and the column keys, or you may use natural ordering for both. 040 * 041 * <p>The {@link #rowKeySet} method returns a {@link SortedSet} and the {@link #rowMap} method 042 * returns a {@link SortedMap}, instead of the {@link Set} and {@link Map} specified by the {@link 043 * Table} interface. 044 * 045 * <p>The views returned by {@link #column}, {@link #columnKeySet()}, and {@link #columnMap()} have 046 * iterators that don't support {@code remove()}. Otherwise, all optional operations are supported. 047 * Null row keys, columns keys, and values are not supported. 048 * 049 * <p>Lookups by row key are often faster than lookups by column key, because the data is stored in 050 * a {@code Map<R, Map<C, V>>}. A method call like {@code column(columnKey).get(rowKey)} still runs 051 * quickly, since the row key is provided. However, {@code column(columnKey).size()} takes longer, 052 * since an iteration across all row keys occurs. 053 * 054 * <p>Because a {@code TreeBasedTable} has unique sorted values for a given row, both {@code 055 * row(rowKey)} and {@code rowMap().get(rowKey)} are {@link SortedMap} instances, instead of the 056 * {@link Map} specified in the {@link Table} interface. 057 * 058 * <p>Note that this implementation is not synchronized. If multiple threads access this table 059 * concurrently and one of the threads modifies the table, it must be synchronized externally. 060 * 061 * <p>See the Guava User Guide article on <a href= 062 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#table">{@code Table}</a>. 063 * 064 * @author Jared Levy 065 * @author Louis Wasserman 066 * @since 7.0 067 */ 068@GwtCompatible(serializable = true) 069@ElementTypesAreNonnullByDefault 070public class TreeBasedTable<R, C, V> extends StandardRowSortedTable<R, C, V> { 071 private final Comparator<? super C> columnComparator; 072 073 private static class Factory<C, V> implements Supplier<TreeMap<C, V>>, Serializable { 074 final Comparator<? super C> comparator; 075 076 Factory(Comparator<? super C> comparator) { 077 this.comparator = comparator; 078 } 079 080 @Override 081 public TreeMap<C, V> get() { 082 return new TreeMap<>(comparator); 083 } 084 085 private static final long serialVersionUID = 0; 086 } 087 088 /** 089 * Creates an empty {@code TreeBasedTable} that uses the natural orderings of both row and column 090 * keys. 091 * 092 * <p>The method signature specifies {@code R extends Comparable} with a raw {@link Comparable}, 093 * instead of {@code R extends Comparable<? super R>}, and the same for {@code C}. That's 094 * necessary to support classes defined without generics. 095 */ 096 public static <R extends Comparable, C extends Comparable, V> TreeBasedTable<R, C, V> create() { 097 return new TreeBasedTable<>(Ordering.natural(), Ordering.natural()); 098 } 099 100 /** 101 * Creates an empty {@code TreeBasedTable} that is ordered by the specified comparators. 102 * 103 * @param rowComparator the comparator that orders the row keys 104 * @param columnComparator the comparator that orders the column keys 105 */ 106 public static <R, C, V> TreeBasedTable<R, C, V> create( 107 Comparator<? super R> rowComparator, Comparator<? super C> columnComparator) { 108 checkNotNull(rowComparator); 109 checkNotNull(columnComparator); 110 return new TreeBasedTable<>(rowComparator, columnComparator); 111 } 112 113 /** 114 * Creates a {@code TreeBasedTable} with the same mappings and sort order as the specified {@code 115 * TreeBasedTable}. 116 */ 117 public static <R, C, V> TreeBasedTable<R, C, V> create(TreeBasedTable<R, C, ? extends V> table) { 118 TreeBasedTable<R, C, V> result = 119 new TreeBasedTable<>(table.rowComparator(), table.columnComparator()); 120 result.putAll(table); 121 return result; 122 } 123 124 TreeBasedTable(Comparator<? super R> rowComparator, Comparator<? super C> columnComparator) { 125 super(new TreeMap<R, Map<C, V>>(rowComparator), new Factory<C, V>(columnComparator)); 126 this.columnComparator = columnComparator; 127 } 128 129 // TODO(jlevy): Move to StandardRowSortedTable? 130 131 /** 132 * Returns the comparator that orders the rows. With natural ordering, {@link Ordering#natural()} 133 * is returned. 134 * 135 * @deprecated Use {@code table.rowKeySet().comparator()} instead. 136 */ 137 @Deprecated 138 public Comparator<? super R> rowComparator() { 139 /* 140 * requireNonNull is safe because the factories require non-null Comparators, which they pass on 141 * to the backing collections. 142 */ 143 return requireNonNull(rowKeySet().comparator()); 144 } 145 146 /** 147 * Returns the comparator that orders the columns. With natural ordering, {@link 148 * Ordering#natural()} is returned. 149 * 150 * @deprecated Store the {@link Comparator} alongside the {@link Table}. Or, if you know that the 151 * {@link Table} contains at least one value, you can retrieve the {@link Comparator} with: 152 * {@code ((SortedMap<C, V>) table.rowMap().values().iterator().next()).comparator();}. 153 */ 154 @Deprecated 155 public Comparator<? super C> columnComparator() { 156 return columnComparator; 157 } 158 159 // TODO(lowasser): make column return a SortedMap 160 161 /** 162 * {@inheritDoc} 163 * 164 * <p>Because a {@code TreeBasedTable} has unique sorted values for a given row, this method 165 * returns a {@link SortedMap}, instead of the {@link Map} specified in the {@link Table} 166 * interface. 167 * 168 * @since 10.0 (<a href="https://github.com/google/guava/wiki/Compatibility" >mostly 169 * source-compatible</a> since 7.0) 170 */ 171 @Override 172 public SortedMap<C, V> row(R rowKey) { 173 return new TreeRow(rowKey); 174 } 175 176 private class TreeRow extends Row implements SortedMap<C, V> { 177 @CheckForNull final C lowerBound; 178 @CheckForNull final C upperBound; 179 180 TreeRow(R rowKey) { 181 this(rowKey, null, null); 182 } 183 184 TreeRow(R rowKey, @CheckForNull C lowerBound, @CheckForNull C upperBound) { 185 super(rowKey); 186 this.lowerBound = lowerBound; 187 this.upperBound = upperBound; 188 checkArgument( 189 lowerBound == null || upperBound == null || compare(lowerBound, upperBound) <= 0); 190 } 191 192 @Override 193 public SortedSet<C> keySet() { 194 return new Maps.SortedKeySet<>(this); 195 } 196 197 @Override 198 public Comparator<? super C> comparator() { 199 return columnComparator(); 200 } 201 202 int compare(Object a, Object b) { 203 // pretend we can compare anything 204 @SuppressWarnings("unchecked") 205 Comparator<Object> cmp = (Comparator<Object>) comparator(); 206 return cmp.compare(a, b); 207 } 208 209 boolean rangeContains(@CheckForNull Object o) { 210 return o != null 211 && (lowerBound == null || compare(lowerBound, o) <= 0) 212 && (upperBound == null || compare(upperBound, o) > 0); 213 } 214 215 @Override 216 public SortedMap<C, V> subMap(C fromKey, C toKey) { 217 checkArgument(rangeContains(checkNotNull(fromKey)) && rangeContains(checkNotNull(toKey))); 218 return new TreeRow(rowKey, fromKey, toKey); 219 } 220 221 @Override 222 public SortedMap<C, V> headMap(C toKey) { 223 checkArgument(rangeContains(checkNotNull(toKey))); 224 return new TreeRow(rowKey, lowerBound, toKey); 225 } 226 227 @Override 228 public SortedMap<C, V> tailMap(C fromKey) { 229 checkArgument(rangeContains(checkNotNull(fromKey))); 230 return new TreeRow(rowKey, fromKey, upperBound); 231 } 232 233 @Override 234 public C firstKey() { 235 updateBackingRowMapField(); 236 if (backingRowMap == null) { 237 throw new NoSuchElementException(); 238 } 239 return ((SortedMap<C, V>) backingRowMap).firstKey(); 240 } 241 242 @Override 243 public C lastKey() { 244 updateBackingRowMapField(); 245 if (backingRowMap == null) { 246 throw new NoSuchElementException(); 247 } 248 return ((SortedMap<C, V>) backingRowMap).lastKey(); 249 } 250 251 @CheckForNull transient SortedMap<C, V> wholeRow; 252 253 // If the row was previously empty, we check if there's a new row here every time we're queried. 254 void updateWholeRowField() { 255 if (wholeRow == null || (wholeRow.isEmpty() && backingMap.containsKey(rowKey))) { 256 wholeRow = (SortedMap<C, V>) backingMap.get(rowKey); 257 } 258 } 259 260 @Override 261 @CheckForNull 262 SortedMap<C, V> computeBackingRowMap() { 263 updateWholeRowField(); 264 SortedMap<C, V> map = wholeRow; 265 if (map != null) { 266 if (lowerBound != null) { 267 map = map.tailMap(lowerBound); 268 } 269 if (upperBound != null) { 270 map = map.headMap(upperBound); 271 } 272 return map; 273 } 274 return null; 275 } 276 277 @Override 278 void maintainEmptyInvariant() { 279 updateWholeRowField(); 280 if (wholeRow != null && wholeRow.isEmpty()) { 281 backingMap.remove(rowKey); 282 wholeRow = null; 283 backingRowMap = null; 284 } 285 } 286 287 @Override 288 public boolean containsKey(@CheckForNull Object key) { 289 return rangeContains(key) && super.containsKey(key); 290 } 291 292 @Override 293 @CheckForNull 294 public V put(C key, V value) { 295 checkArgument(rangeContains(checkNotNull(key))); 296 return super.put(key, value); 297 } 298 } 299 300 // rowKeySet() and rowMap() are defined here so they appear in the Javadoc. 301 302 @Override 303 public SortedSet<R> rowKeySet() { 304 return super.rowKeySet(); 305 } 306 307 @Override 308 public SortedMap<R, Map<C, V>> rowMap() { 309 return super.rowMap(); 310 } 311 312 /** Overridden column iterator to return columns values in globally sorted order. */ 313 @Override 314 Iterator<C> createColumnKeyIterator() { 315 Comparator<? super C> comparator = columnComparator(); 316 317 Iterator<C> merged = 318 Iterators.mergeSorted( 319 Iterables.transform( 320 backingMap.values(), (Map<C, V> input) -> input.keySet().iterator()), 321 comparator); 322 323 return new AbstractIterator<C>() { 324 @CheckForNull C lastValue; 325 326 @Override 327 @CheckForNull 328 protected C computeNext() { 329 while (merged.hasNext()) { 330 C next = merged.next(); 331 boolean duplicate = lastValue != null && comparator.compare(next, lastValue) == 0; 332 333 // Keep looping till we find a non-duplicate value. 334 if (!duplicate) { 335 lastValue = next; 336 return lastValue; 337 } 338 } 339 340 lastValue = null; // clear reference to unused data 341 return endOfData(); 342 } 343 }; 344 } 345 346 private static final long serialVersionUID = 0; 347}