1 /* 2 * Copyright (C) 2009 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.base; 18 19 import static com.google.common.base.Preconditions.checkArgument; 20 import static com.google.common.base.Preconditions.checkNotNull; 21 22 import com.google.common.annotations.Beta; 23 import com.google.common.annotations.GwtCompatible; 24 import com.google.common.annotations.GwtIncompatible; 25 26 import java.util.ArrayList; 27 import java.util.Collections; 28 import java.util.Iterator; 29 import java.util.LinkedHashMap; 30 import java.util.List; 31 import java.util.Map; 32 import java.util.regex.Matcher; 33 import java.util.regex.Pattern; 34 35 import javax.annotation.CheckReturnValue; 36 37 /** 38 * Extracts non-overlapping substrings from an input string, typically by 39 * recognizing appearances of a <i>separator</i> sequence. This separator can be 40 * specified as a single {@linkplain #on(char) character}, fixed {@linkplain 41 * #on(String) string}, {@linkplain #onPattern regular expression} or {@link 42 * #on(CharMatcher) CharMatcher} instance. Or, instead of using a separator at 43 * all, a splitter can extract adjacent substrings of a given {@linkplain 44 * #fixedLength fixed length}. 45 * 46 * <p>For example, this expression: <pre> {@code 47 * 48 * Splitter.on(',').split("foo,bar,qux")}</pre> 49 * 50 * ... produces an {@code Iterable} containing {@code "foo"}, {@code "bar"} and 51 * {@code "qux"}, in that order. 52 * 53 * <p>By default, {@code Splitter}'s behavior is simplistic and unassuming. The 54 * following expression: <pre> {@code 55 * 56 * Splitter.on(',').split(" foo,,, bar ,")}</pre> 57 * 58 * ... yields the substrings {@code [" foo", "", "", " bar ", ""]}. If this 59 * is not the desired behavior, use configuration methods to obtain a <i>new</i> 60 * splitter instance with modified behavior: <pre> {@code 61 * 62 * private static final Splitter MY_SPLITTER = Splitter.on(',') 63 * .trimResults() 64 * .omitEmptyStrings();}</pre> 65 * 66 * <p>Now {@code MY_SPLITTER.split("foo,,, bar ,")} returns just {@code ["foo", 67 * "bar"]}. Note that the order in which these configuration methods are called 68 * is never significant. 69 * 70 * <p><b>Warning:</b> Splitter instances are immutable. Invoking a configuration 71 * method has no effect on the receiving instance; you must store and use the 72 * new splitter instance it returns instead. <pre> {@code 73 * 74 * // Do NOT do this 75 * Splitter splitter = Splitter.on('/'); 76 * splitter.trimResults(); // does nothing! 77 * return splitter.split("wrong / wrong / wrong");}</pre> 78 * 79 * <p>For separator-based splitters that do not use {@code omitEmptyStrings}, an 80 * input string containing {@code n} occurrences of the separator naturally 81 * yields an iterable of size {@code n + 1}. So if the separator does not occur 82 * anywhere in the input, a single substring is returned containing the entire 83 * input. Consequently, all splitters split the empty string to {@code [""]} 84 * (note: even fixed-length splitters). 85 * 86 * <p>Splitter instances are thread-safe immutable, and are therefore safe to 87 * store as {@code static final} constants. 88 * 89 * <p>The {@link Joiner} class provides the inverse operation to splitting, but 90 * note that a round-trip between the two should be assumed to be lossy. 91 * 92 * <p>See the Guava User Guide article on <a href= 93 * "http://code.google.com/p/guava-libraries/wiki/StringsExplained#Splitter"> 94 * {@code Splitter}</a>. 95 * 96 * @author Julien Silland 97 * @author Jesse Wilson 98 * @author Kevin Bourrillion 99 * @author Louis Wasserman 100 * @since 1.0 101 */ 102 @GwtCompatible(emulated = true) 103 public final class Splitter { 104 private final CharMatcher trimmer; 105 private final boolean omitEmptyStrings; 106 private final Strategy strategy; 107 private final int limit; 108 109 private Splitter(Strategy strategy) { 110 this(strategy, false, CharMatcher.NONE, Integer.MAX_VALUE); 111 } 112 113 private Splitter(Strategy strategy, boolean omitEmptyStrings, 114 CharMatcher trimmer, int limit) { 115 this.strategy = strategy; 116 this.omitEmptyStrings = omitEmptyStrings; 117 this.trimmer = trimmer; 118 this.limit = limit; 119 } 120 121 /** 122 * Returns a splitter that uses the given single-character separator. For 123 * example, {@code Splitter.on(',').split("foo,,bar")} returns an iterable 124 * containing {@code ["foo", "", "bar"]}. 125 * 126 * @param separator the character to recognize as a separator 127 * @return a splitter, with default settings, that recognizes that separator 128 */ 129 public static Splitter on(char separator) { 130 return on(CharMatcher.is(separator)); 131 } 132 133 /** 134 * Returns a splitter that considers any single character matched by the 135 * given {@code CharMatcher} to be a separator. For example, {@code 136 * Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux")} returns an 137 * iterable containing {@code ["foo", "", "bar", "quux"]}. 138 * 139 * @param separatorMatcher a {@link CharMatcher} that determines whether a 140 * character is a separator 141 * @return a splitter, with default settings, that uses this matcher 142 */ 143 public static Splitter on(final CharMatcher separatorMatcher) { 144 checkNotNull(separatorMatcher); 145 146 return new Splitter(new Strategy() { 147 @Override public SplittingIterator iterator( 148 Splitter splitter, final CharSequence toSplit) { 149 return new SplittingIterator(splitter, toSplit) { 150 @Override int separatorStart(int start) { 151 return separatorMatcher.indexIn(toSplit, start); 152 } 153 154 @Override int separatorEnd(int separatorPosition) { 155 return separatorPosition + 1; 156 } 157 }; 158 } 159 }); 160 } 161 162 /** 163 * Returns a splitter that uses the given fixed string as a separator. For 164 * example, {@code Splitter.on(", ").split("foo, bar,baz")} returns an 165 * iterable containing {@code ["foo", "bar,baz"]}. 166 * 167 * @param separator the literal, nonempty string to recognize as a separator 168 * @return a splitter, with default settings, that recognizes that separator 169 */ 170 public static Splitter on(final String separator) { 171 checkArgument(separator.length() != 0, 172 "The separator may not be the empty string."); 173 174 return new Splitter(new Strategy() { 175 @Override public SplittingIterator iterator( 176 Splitter splitter, CharSequence toSplit) { 177 return new SplittingIterator(splitter, toSplit) { 178 @Override public int separatorStart(int start) { 179 int separatorLength = separator.length(); 180 181 positions: 182 for (int p = start, last = toSplit.length() - separatorLength; 183 p <= last; p++) { 184 for (int i = 0; i < separatorLength; i++) { 185 if (toSplit.charAt(i + p) != separator.charAt(i)) { 186 continue positions; 187 } 188 } 189 return p; 190 } 191 return -1; 192 } 193 194 @Override public int separatorEnd(int separatorPosition) { 195 return separatorPosition + separator.length(); 196 } 197 }; 198 } 199 }); 200 } 201 202 /** 203 * Returns a splitter that considers any subsequence matching {@code 204 * pattern} to be a separator. For example, {@code 205 * Splitter.on(Pattern.compile("\r?\n")).split(entireFile)} splits a string 206 * into lines whether it uses DOS-style or UNIX-style line terminators. 207 * 208 * @param separatorPattern the pattern that determines whether a subsequence 209 * is a separator. This pattern may not match the empty string. 210 * @return a splitter, with default settings, that uses this pattern 211 * @throws IllegalArgumentException if {@code separatorPattern} matches the 212 * empty string 213 */ 214 @GwtIncompatible("java.util.regex") 215 public static Splitter on(final Pattern separatorPattern) { 216 checkNotNull(separatorPattern); 217 checkArgument(!separatorPattern.matcher("").matches(), 218 "The pattern may not match the empty string: %s", separatorPattern); 219 220 return new Splitter(new Strategy() { 221 @Override public SplittingIterator iterator( 222 final Splitter splitter, CharSequence toSplit) { 223 final Matcher matcher = separatorPattern.matcher(toSplit); 224 return new SplittingIterator(splitter, toSplit) { 225 @Override public int separatorStart(int start) { 226 return matcher.find(start) ? matcher.start() : -1; 227 } 228 229 @Override public int separatorEnd(int separatorPosition) { 230 return matcher.end(); 231 } 232 }; 233 } 234 }); 235 } 236 237 /** 238 * Returns a splitter that considers any subsequence matching a given 239 * pattern (regular expression) to be a separator. For example, {@code 240 * Splitter.onPattern("\r?\n").split(entireFile)} splits a string into lines 241 * whether it uses DOS-style or UNIX-style line terminators. This is 242 * equivalent to {@code Splitter.on(Pattern.compile(pattern))}. 243 * 244 * @param separatorPattern the pattern that determines whether a subsequence 245 * is a separator. This pattern may not match the empty string. 246 * @return a splitter, with default settings, that uses this pattern 247 * @throws java.util.regex.PatternSyntaxException if {@code separatorPattern} 248 * is a malformed expression 249 * @throws IllegalArgumentException if {@code separatorPattern} matches the 250 * empty string 251 */ 252 @GwtIncompatible("java.util.regex") 253 public static Splitter onPattern(String separatorPattern) { 254 return on(Pattern.compile(separatorPattern)); 255 } 256 257 /** 258 * Returns a splitter that divides strings into pieces of the given length. 259 * For example, {@code Splitter.fixedLength(2).split("abcde")} returns an 260 * iterable containing {@code ["ab", "cd", "e"]}. The last piece can be 261 * smaller than {@code length} but will never be empty. 262 * 263 * <p><b>Exception:</b> for consistency with separator-based splitters, {@code 264 * split("")} does not yield an empty iterable, but an iterable containing 265 * {@code ""}. This is the only case in which {@code 266 * Iterables.size(split(input))} does not equal {@code 267 * IntMath.divide(input.length(), length, CEILING)}. To avoid this behavior, 268 * use {@code omitEmptyStrings}. 269 * 270 * @param length the desired length of pieces after splitting, a positive 271 * integer 272 * @return a splitter, with default settings, that can split into fixed sized 273 * pieces 274 * @throws IllegalArgumentException if {@code length} is zero or negative 275 */ 276 public static Splitter fixedLength(final int length) { 277 checkArgument(length > 0, "The length may not be less than 1"); 278 279 return new Splitter(new Strategy() { 280 @Override public SplittingIterator iterator( 281 final Splitter splitter, CharSequence toSplit) { 282 return new SplittingIterator(splitter, toSplit) { 283 @Override public int separatorStart(int start) { 284 int nextChunkStart = start + length; 285 return (nextChunkStart < toSplit.length() ? nextChunkStart : -1); 286 } 287 288 @Override public int separatorEnd(int separatorPosition) { 289 return separatorPosition; 290 } 291 }; 292 } 293 }); 294 } 295 296 /** 297 * Returns a splitter that behaves equivalently to {@code this} splitter, but 298 * automatically omits empty strings from the results. For example, {@code 299 * Splitter.on(',').omitEmptyStrings().split(",a,,,b,c,,")} returns an 300 * iterable containing only {@code ["a", "b", "c"]}. 301 * 302 * <p>If either {@code trimResults} option is also specified when creating a 303 * splitter, that splitter always trims results first before checking for 304 * emptiness. So, for example, {@code 305 * Splitter.on(':').omitEmptyStrings().trimResults().split(": : : ")} returns 306 * an empty iterable. 307 * 308 * <p>Note that it is ordinarily not possible for {@link #split(CharSequence)} 309 * to return an empty iterable, but when using this option, it can (if the 310 * input sequence consists of nothing but separators). 311 * 312 * @return a splitter with the desired configuration 313 */ 314 @CheckReturnValue 315 public Splitter omitEmptyStrings() { 316 return new Splitter(strategy, true, trimmer, limit); 317 } 318 319 /** 320 * Returns a splitter that behaves equivalently to {@code this} splitter but 321 * stops splitting after it reaches the limit. 322 * The limit defines the maximum number of items returned by the iterator. 323 * 324 * <p>For example, 325 * {@code Splitter.on(',').limit(3).split("a,b,c,d")} returns an iterable 326 * containing {@code ["a", "b", "c,d"]}. When omitting empty strings, the 327 * omitted strings do no count. Hence, 328 * {@code Splitter.on(',').limit(3).omitEmptyStrings().split("a,,,b,,,c,d")} 329 * returns an iterable containing {@code ["a", "b", "c,d"}. 330 * When trim is requested, all entries, including the last are trimmed. Hence 331 * {@code Splitter.on(',').limit(3).trimResults().split(" a , b , c , d ")} 332 * results in @{code ["a", "b", "c , d"]}. 333 * 334 * @param limit the maximum number of items returns 335 * @return a splitter with the desired configuration 336 * @since 9.0 337 */ 338 @CheckReturnValue 339 public Splitter limit(int limit) { 340 checkArgument(limit > 0, "must be greater than zero: %s", limit); 341 return new Splitter(strategy, omitEmptyStrings, trimmer, limit); 342 } 343 344 /** 345 * Returns a splitter that behaves equivalently to {@code this} splitter, but 346 * automatically removes leading and trailing {@linkplain 347 * CharMatcher#WHITESPACE whitespace} from each returned substring; equivalent 348 * to {@code trimResults(CharMatcher.WHITESPACE)}. For example, {@code 349 * Splitter.on(',').trimResults().split(" a, b ,c ")} returns an iterable 350 * containing {@code ["a", "b", "c"]}. 351 * 352 * @return a splitter with the desired configuration 353 */ 354 @CheckReturnValue 355 public Splitter trimResults() { 356 return trimResults(CharMatcher.WHITESPACE); 357 } 358 359 /** 360 * Returns a splitter that behaves equivalently to {@code this} splitter, but 361 * removes all leading or trailing characters matching the given {@code 362 * CharMatcher} from each returned substring. For example, {@code 363 * Splitter.on(',').trimResults(CharMatcher.is('_')).split("_a ,_b_ ,c__")} 364 * returns an iterable containing {@code ["a ", "b_ ", "c"]}. 365 * 366 * @param trimmer a {@link CharMatcher} that determines whether a character 367 * should be removed from the beginning/end of a subsequence 368 * @return a splitter with the desired configuration 369 */ 370 // TODO(kevinb): throw if a trimmer was already specified! 371 @CheckReturnValue 372 public Splitter trimResults(CharMatcher trimmer) { 373 checkNotNull(trimmer); 374 return new Splitter(strategy, omitEmptyStrings, trimmer, limit); 375 } 376 377 /** 378 * Splits {@code sequence} into string components and makes them available 379 * through an {@link Iterator}, which may be lazily evaluated. If you want 380 * an eagerly computed {@link List}, use {@link #splitToList(CharSequence)}. 381 * 382 * @param sequence the sequence of characters to split 383 * @return an iteration over the segments split from the parameter. 384 */ 385 public Iterable<String> split(final CharSequence sequence) { 386 checkNotNull(sequence); 387 388 return new Iterable<String>() { 389 @Override public Iterator<String> iterator() { 390 return splittingIterator(sequence); 391 } 392 @Override public String toString() { 393 return Joiner.on(", ") 394 .appendTo(new StringBuilder().append('['), this) 395 .append(']') 396 .toString(); 397 } 398 }; 399 } 400 401 private Iterator<String> splittingIterator(CharSequence sequence) { 402 return strategy.iterator(this, sequence); 403 } 404 405 /** 406 * Splits {@code sequence} into string components and returns them as 407 * an immutable list. If you want an {@link Iterable} which may be lazily 408 * evaluated, use {@link #split(CharSequence)}. 409 * 410 * @param sequence the sequence of characters to split 411 * @return an immutable list of the segments split from the parameter 412 * @since 15.0 413 */ 414 @Beta 415 public List<String> splitToList(CharSequence sequence) { 416 checkNotNull(sequence); 417 418 Iterator<String> iterator = splittingIterator(sequence); 419 List<String> result = new ArrayList<String>(); 420 421 while (iterator.hasNext()) { 422 result.add(iterator.next()); 423 } 424 425 return Collections.unmodifiableList(result); 426 } 427 428 /** 429 * Returns a {@code MapSplitter} which splits entries based on this splitter, 430 * and splits entries into keys and values using the specified separator. 431 * 432 * @since 10.0 433 */ 434 @CheckReturnValue 435 @Beta 436 public MapSplitter withKeyValueSeparator(String separator) { 437 return withKeyValueSeparator(on(separator)); 438 } 439 440 /** 441 * Returns a {@code MapSplitter} which splits entries based on this splitter, 442 * and splits entries into keys and values using the specified separator. 443 * 444 * @since 14.0 445 */ 446 @CheckReturnValue 447 @Beta 448 public MapSplitter withKeyValueSeparator(char separator) { 449 return withKeyValueSeparator(on(separator)); 450 } 451 452 /** 453 * Returns a {@code MapSplitter} which splits entries based on this splitter, 454 * and splits entries into keys and values using the specified key-value 455 * splitter. 456 * 457 * @since 10.0 458 */ 459 @CheckReturnValue 460 @Beta 461 public MapSplitter withKeyValueSeparator(Splitter keyValueSplitter) { 462 return new MapSplitter(this, keyValueSplitter); 463 } 464 465 /** 466 * An object that splits strings into maps as {@code Splitter} splits 467 * iterables and lists. Like {@code Splitter}, it is thread-safe and 468 * immutable. 469 * 470 * @since 10.0 471 */ 472 @Beta 473 public static final class MapSplitter { 474 private static final String INVALID_ENTRY_MESSAGE = 475 "Chunk [%s] is not a valid entry"; 476 private final Splitter outerSplitter; 477 private final Splitter entrySplitter; 478 479 private MapSplitter(Splitter outerSplitter, Splitter entrySplitter) { 480 this.outerSplitter = outerSplitter; // only "this" is passed 481 this.entrySplitter = checkNotNull(entrySplitter); 482 } 483 484 /** 485 * Splits {@code sequence} into substrings, splits each substring into 486 * an entry, and returns an unmodifiable map with each of the entries. For 487 * example, <code> 488 * Splitter.on(';').trimResults().withKeyValueSeparator("=>") 489 * .split("a=>b ; c=>b") 490 * </code> will return a mapping from {@code "a"} to {@code "b"} and 491 * {@code "c"} to {@code b}. 492 * 493 * <p>The returned map preserves the order of the entries from 494 * {@code sequence}. 495 * 496 * @throws IllegalArgumentException if the specified sequence does not split 497 * into valid map entries, or if there are duplicate keys 498 */ 499 public Map<String, String> split(CharSequence sequence) { 500 Map<String, String> map = new LinkedHashMap<String, String>(); 501 for (String entry : outerSplitter.split(sequence)) { 502 Iterator<String> entryFields = entrySplitter.splittingIterator(entry); 503 504 checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); 505 String key = entryFields.next(); 506 checkArgument(!map.containsKey(key), "Duplicate key [%s] found.", key); 507 508 checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); 509 String value = entryFields.next(); 510 map.put(key, value); 511 512 checkArgument(!entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); 513 } 514 return Collections.unmodifiableMap(map); 515 } 516 } 517 518 private interface Strategy { 519 Iterator<String> iterator(Splitter splitter, CharSequence toSplit); 520 } 521 522 private abstract static class SplittingIterator extends AbstractIterator<String> { 523 final CharSequence toSplit; 524 final CharMatcher trimmer; 525 final boolean omitEmptyStrings; 526 527 /** 528 * Returns the first index in {@code toSplit} at or after {@code start} 529 * that contains the separator. 530 */ 531 abstract int separatorStart(int start); 532 533 /** 534 * Returns the first index in {@code toSplit} after {@code 535 * separatorPosition} that does not contain a separator. This method is only 536 * invoked after a call to {@code separatorStart}. 537 */ 538 abstract int separatorEnd(int separatorPosition); 539 540 int offset = 0; 541 int limit; 542 543 protected SplittingIterator(Splitter splitter, CharSequence toSplit) { 544 this.trimmer = splitter.trimmer; 545 this.omitEmptyStrings = splitter.omitEmptyStrings; 546 this.limit = splitter.limit; 547 this.toSplit = toSplit; 548 } 549 550 @Override protected String computeNext() { 551 /* 552 * The returned string will be from the end of the last match to the 553 * beginning of the next one. nextStart is the start position of the 554 * returned substring, while offset is the place to start looking for a 555 * separator. 556 */ 557 int nextStart = offset; 558 while (offset != -1) { 559 int start = nextStart; 560 int end; 561 562 int separatorPosition = separatorStart(offset); 563 if (separatorPosition == -1) { 564 end = toSplit.length(); 565 offset = -1; 566 } else { 567 end = separatorPosition; 568 offset = separatorEnd(separatorPosition); 569 } 570 if (offset == nextStart) { 571 /* 572 * This occurs when some pattern has an empty match, even if it 573 * doesn't match the empty string -- for example, if it requires 574 * lookahead or the like. The offset must be increased to look for 575 * separators beyond this point, without changing the start position 576 * of the next returned substring -- so nextStart stays the same. 577 */ 578 offset++; 579 if (offset >= toSplit.length()) { 580 offset = -1; 581 } 582 continue; 583 } 584 585 while (start < end && trimmer.matches(toSplit.charAt(start))) { 586 start++; 587 } 588 while (end > start && trimmer.matches(toSplit.charAt(end - 1))) { 589 end--; 590 } 591 592 if (omitEmptyStrings && start == end) { 593 // Don't include the (unused) separator in next split string. 594 nextStart = offset; 595 continue; 596 } 597 598 if (limit == 1) { 599 // The limit has been reached, return the rest of the string as the 600 // final item. This is tested after empty string removal so that 601 // empty strings do not count towards the limit. 602 end = toSplit.length(); 603 offset = -1; 604 // Since we may have changed the end, we need to trim it again. 605 while (end > start && trimmer.matches(toSplit.charAt(end - 1))) { 606 end--; 607 } 608 } else { 609 limit--; 610 } 611 612 return toSplit.subSequence(start, end).toString(); 613 } 614 return endOfData(); 615 } 616 } 617 } 618