001/* 002 * Copyright (C) 2009 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.base; 016 017import static com.google.common.base.Preconditions.checkArgument; 018import static com.google.common.base.Preconditions.checkNotNull; 019 020import com.google.common.annotations.GwtCompatible; 021import com.google.common.annotations.GwtIncompatible; 022import java.util.ArrayList; 023import java.util.Collections; 024import java.util.Iterator; 025import java.util.LinkedHashMap; 026import java.util.List; 027import java.util.Map; 028import java.util.regex.Pattern; 029import java.util.stream.Stream; 030import java.util.stream.StreamSupport; 031import javax.annotation.CheckForNull; 032 033/** 034 * Extracts non-overlapping substrings from an input string, typically by recognizing appearances of 035 * a <i>separator</i> sequence. This separator can be specified as a single {@linkplain #on(char) 036 * character}, fixed {@linkplain #on(String) string}, {@linkplain #onPattern regular expression} or 037 * {@link #on(CharMatcher) CharMatcher} instance. Or, instead of using a separator at all, a 038 * splitter can extract adjacent substrings of a given {@linkplain #fixedLength fixed length}. 039 * 040 * <p>For example, this expression: 041 * 042 * <pre>{@code 043 * Splitter.on(',').split("foo,bar,qux") 044 * }</pre> 045 * 046 * ... produces an {@code Iterable} containing {@code "foo"}, {@code "bar"} and {@code "qux"}, in 047 * that order. 048 * 049 * <p>By default, {@code Splitter}'s behavior is simplistic and unassuming. The following 050 * expression: 051 * 052 * <pre>{@code 053 * Splitter.on(',').split(" foo,,, bar ,") 054 * }</pre> 055 * 056 * ... yields the substrings {@code [" foo", "", "", " bar ", ""]}. If this is not the desired 057 * behavior, use configuration methods to obtain a <i>new</i> splitter instance with modified 058 * behavior: 059 * 060 * <pre>{@code 061 * private static final Splitter MY_SPLITTER = Splitter.on(',') 062 * .trimResults() 063 * .omitEmptyStrings(); 064 * }</pre> 065 * 066 * <p>Now {@code MY_SPLITTER.split("foo,,, bar ,")} returns just {@code ["foo", "bar"]}. Note that 067 * the order in which these configuration methods are called is never significant. 068 * 069 * <p><b>Warning:</b> Splitter instances are immutable. Invoking a configuration method has no 070 * effect on the receiving instance; you must store and use the new splitter instance it returns 071 * instead. 072 * 073 * <pre>{@code 074 * // Do NOT do this 075 * Splitter splitter = Splitter.on('/'); 076 * splitter.trimResults(); // does nothing! 077 * return splitter.split("wrong / wrong / wrong"); 078 * }</pre> 079 * 080 * <p>For separator-based splitters that do not use {@code omitEmptyStrings}, an input string 081 * containing {@code n} occurrences of the separator naturally yields an iterable of size {@code n + 082 * 1}. So if the separator does not occur anywhere in the input, a single substring is returned 083 * containing the entire input. Consequently, all splitters split the empty string to {@code [""]} 084 * (note: even fixed-length splitters). 085 * 086 * <p>Splitter instances are thread-safe immutable, and are therefore safe to store as {@code static 087 * final} constants. 088 * 089 * <p>The {@link Joiner} class provides the inverse operation to splitting, but note that a 090 * round-trip between the two should be assumed to be lossy. 091 * 092 * <p>See the Guava User Guide article on <a 093 * href="https://github.com/google/guava/wiki/StringsExplained#splitter">{@code Splitter}</a>. 094 * 095 * @author Julien Silland 096 * @author Jesse Wilson 097 * @author Kevin Bourrillion 098 * @author Louis Wasserman 099 * @since 1.0 100 */ 101@GwtCompatible(emulated = true) 102@ElementTypesAreNonnullByDefault 103public 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, CharMatcher trimmer, int limit) { 114 this.strategy = strategy; 115 this.omitEmptyStrings = omitEmptyStrings; 116 this.trimmer = trimmer; 117 this.limit = limit; 118 } 119 120 /** 121 * Returns a splitter that uses the given single-character separator. For example, {@code 122 * Splitter.on(',').split("foo,,bar")} returns an iterable containing {@code ["foo", "", "bar"]}. 123 * 124 * @param separator the character to recognize as a separator 125 * @return a splitter, with default settings, that recognizes that separator 126 */ 127 public static Splitter on(char separator) { 128 return on(CharMatcher.is(separator)); 129 } 130 131 /** 132 * Returns a splitter that considers any single character matched by the given {@code CharMatcher} 133 * to be a separator. For example, {@code 134 * Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux")} returns an iterable containing 135 * {@code ["foo", "", "bar", "quux"]}. 136 * 137 * @param separatorMatcher a {@link CharMatcher} that determines whether a character is a 138 * separator 139 * @return a splitter, with default settings, that uses this matcher 140 */ 141 public static Splitter on(final CharMatcher separatorMatcher) { 142 checkNotNull(separatorMatcher); 143 144 return new Splitter( 145 new Strategy() { 146 @Override 147 public SplittingIterator iterator(Splitter splitter, final CharSequence toSplit) { 148 return new SplittingIterator(splitter, toSplit) { 149 @Override 150 int separatorStart(int start) { 151 return separatorMatcher.indexIn(toSplit, start); 152 } 153 154 @Override 155 int separatorEnd(int separatorPosition) { 156 return separatorPosition + 1; 157 } 158 }; 159 } 160 }); 161 } 162 163 /** 164 * Returns a splitter that uses the given fixed string as a separator. For example, {@code 165 * Splitter.on(", ").split("foo, bar,baz")} returns an iterable containing {@code ["foo", 166 * "bar,baz"]}. 167 * 168 * @param separator the literal, nonempty string to recognize as a separator 169 * @return a splitter, with default settings, that recognizes that separator 170 */ 171 public static Splitter on(final String separator) { 172 checkArgument(separator.length() != 0, "The separator may not be the empty string."); 173 if (separator.length() == 1) { 174 return Splitter.on(separator.charAt(0)); 175 } 176 return new Splitter( 177 new Strategy() { 178 @Override 179 public SplittingIterator iterator(Splitter splitter, CharSequence toSplit) { 180 return new SplittingIterator(splitter, toSplit) { 181 @Override 182 public int separatorStart(int start) { 183 int separatorLength = separator.length(); 184 185 positions: 186 for (int p = start, last = toSplit.length() - separatorLength; p <= last; p++) { 187 for (int i = 0; i < separatorLength; i++) { 188 if (toSplit.charAt(i + p) != separator.charAt(i)) { 189 continue positions; 190 } 191 } 192 return p; 193 } 194 return -1; 195 } 196 197 @Override 198 public int separatorEnd(int separatorPosition) { 199 return separatorPosition + separator.length(); 200 } 201 }; 202 } 203 }); 204 } 205 206 /** 207 * Returns a splitter that considers any subsequence matching {@code pattern} to be a separator. 208 * For example, {@code Splitter.on(Pattern.compile("\r?\n")).split(entireFile)} splits a string 209 * into lines whether it uses DOS-style or UNIX-style line terminators. 210 * 211 * @param separatorPattern the pattern that determines whether a subsequence is a separator. This 212 * pattern may not match the empty string. 213 * @return a splitter, with default settings, that uses this pattern 214 * @throws IllegalArgumentException if {@code separatorPattern} matches the empty string 215 */ 216 @GwtIncompatible // java.util.regex 217 public static Splitter on(Pattern separatorPattern) { 218 return onPatternInternal(new JdkPattern(separatorPattern)); 219 } 220 221 /** Internal utility; see {@link #on(Pattern)} instead. */ 222 static Splitter onPatternInternal(final CommonPattern separatorPattern) { 223 checkArgument( 224 !separatorPattern.matcher("").matches(), 225 "The pattern may not match the empty string: %s", 226 separatorPattern); 227 228 return new Splitter( 229 new Strategy() { 230 @Override 231 public SplittingIterator iterator(final Splitter splitter, CharSequence toSplit) { 232 final CommonMatcher matcher = separatorPattern.matcher(toSplit); 233 return new SplittingIterator(splitter, toSplit) { 234 @Override 235 public int separatorStart(int start) { 236 return matcher.find(start) ? matcher.start() : -1; 237 } 238 239 @Override 240 public int separatorEnd(int separatorPosition) { 241 return matcher.end(); 242 } 243 }; 244 } 245 }); 246 } 247 248 /** 249 * Returns a splitter that considers any subsequence matching a given pattern (regular expression) 250 * to be a separator. For example, {@code Splitter.onPattern("\r?\n").split(entireFile)} splits a 251 * string into lines whether it uses DOS-style or UNIX-style line terminators. This is equivalent 252 * to {@code Splitter.on(Pattern.compile(pattern))}. 253 * 254 * @param separatorPattern the pattern that determines whether a subsequence is a separator. This 255 * pattern may not match the empty string. 256 * @return a splitter, with default settings, that uses this pattern 257 * @throws IllegalArgumentException if {@code separatorPattern} matches the empty string or is a 258 * malformed expression 259 */ 260 @GwtIncompatible // java.util.regex 261 public static Splitter onPattern(String separatorPattern) { 262 return onPatternInternal(Platform.compilePattern(separatorPattern)); 263 } 264 265 /** 266 * Returns a splitter that divides strings into pieces of the given length. For example, {@code 267 * Splitter.fixedLength(2).split("abcde")} returns an iterable containing {@code ["ab", "cd", 268 * "e"]}. The last piece can be smaller than {@code length} but will never be empty. 269 * 270 * <p><b>Note:</b> if {@link #fixedLength} is used in conjunction with {@link #limit}, the final 271 * split piece <i>may be longer than the specified fixed length</i>. This is because the splitter 272 * will <i>stop splitting when the limit is reached</i>, and just return the final piece as-is. 273 * 274 * <p><b>Exception:</b> for consistency with separator-based splitters, {@code split("")} does not 275 * yield an empty iterable, but an iterable containing {@code ""}. This is the only case in which 276 * {@code Iterables.size(split(input))} does not equal {@code IntMath.divide(input.length(), 277 * length, CEILING)}. To avoid this behavior, use {@code omitEmptyStrings}. 278 * 279 * @param length the desired length of pieces after splitting, a positive integer 280 * @return a splitter, with default settings, that can split into fixed sized pieces 281 * @throws IllegalArgumentException if {@code length} is zero or negative 282 */ 283 public static Splitter fixedLength(final int length) { 284 checkArgument(length > 0, "The length may not be less than 1"); 285 286 return new Splitter( 287 new Strategy() { 288 @Override 289 public SplittingIterator iterator(final Splitter splitter, CharSequence toSplit) { 290 return new SplittingIterator(splitter, toSplit) { 291 @Override 292 public int separatorStart(int start) { 293 int nextChunkStart = start + length; 294 return (nextChunkStart < toSplit.length() ? nextChunkStart : -1); 295 } 296 297 @Override 298 public int separatorEnd(int separatorPosition) { 299 return separatorPosition; 300 } 301 }; 302 } 303 }); 304 } 305 306 /** 307 * Returns a splitter that behaves equivalently to {@code this} splitter, but automatically omits 308 * empty strings from the results. For example, {@code 309 * Splitter.on(',').omitEmptyStrings().split(",a,,,b,c,,")} returns an iterable containing only 310 * {@code ["a", "b", "c"]}. 311 * 312 * <p>If either {@code trimResults} option is also specified when creating a splitter, that 313 * splitter always trims results first before checking for emptiness. So, for example, {@code 314 * Splitter.on(':').omitEmptyStrings().trimResults().split(": : : ")} returns an empty iterable. 315 * 316 * <p>Note that it is ordinarily not possible for {@link #split(CharSequence)} to return an empty 317 * iterable, but when using this option, it can (if the input sequence consists of nothing but 318 * separators). 319 * 320 * @return a splitter with the desired configuration 321 */ 322 public Splitter omitEmptyStrings() { 323 return new Splitter(strategy, true, trimmer, limit); 324 } 325 326 /** 327 * Returns a splitter that behaves equivalently to {@code this} splitter but stops splitting after 328 * it reaches the limit. The limit defines the maximum number of items returned by the iterator, 329 * or the maximum size of the list returned by {@link #splitToList}. 330 * 331 * <p>For example, {@code Splitter.on(',').limit(3).split("a,b,c,d")} returns an iterable 332 * containing {@code ["a", "b", "c,d"]}. When omitting empty strings, the omitted strings do not 333 * count. Hence, {@code Splitter.on(',').limit(3).omitEmptyStrings().split("a,,,b,,,c,d")} returns 334 * an iterable containing {@code ["a", "b", "c,d"]}. When trim is requested, all entries are 335 * trimmed, including the last. Hence {@code Splitter.on(',').limit(3).trimResults().split(" a , b 336 * , c , d ")} results in {@code ["a", "b", "c , d"]}. 337 * 338 * @param maxItems the maximum number of items returned 339 * @return a splitter with the desired configuration 340 * @since 9.0 341 */ 342 public Splitter limit(int maxItems) { 343 checkArgument(maxItems > 0, "must be greater than zero: %s", maxItems); 344 return new Splitter(strategy, omitEmptyStrings, trimmer, maxItems); 345 } 346 347 /** 348 * Returns a splitter that behaves equivalently to {@code this} splitter, but automatically 349 * removes leading and trailing {@linkplain CharMatcher#whitespace whitespace} from each returned 350 * substring; equivalent to {@code trimResults(CharMatcher.whitespace())}. For example, {@code 351 * Splitter.on(',').trimResults().split(" a, b ,c ")} returns an iterable containing {@code ["a", 352 * "b", "c"]}. 353 * 354 * @return a splitter with the desired configuration 355 */ 356 public Splitter trimResults() { 357 return trimResults(CharMatcher.whitespace()); 358 } 359 360 /** 361 * Returns a splitter that behaves equivalently to {@code this} splitter, but removes all leading 362 * or trailing characters matching the given {@code CharMatcher} from each returned substring. For 363 * example, {@code 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 should be removed from 367 * 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 public Splitter trimResults(CharMatcher trimmer) { 372 checkNotNull(trimmer); 373 return new Splitter(strategy, omitEmptyStrings, trimmer, limit); 374 } 375 376 /** 377 * Splits {@code sequence} into string components and makes them available through an {@link 378 * Iterator}, which may be lazily evaluated. If you want an eagerly computed {@link List}, use 379 * {@link #splitToList(CharSequence)}. Java 8+ users may prefer {@link #splitToStream} instead. 380 * 381 * @param sequence the sequence of characters to split 382 * @return an iteration over the segments split from the parameter 383 */ 384 public Iterable<String> split(final CharSequence sequence) { 385 checkNotNull(sequence); 386 387 return new Iterable<String>() { 388 @Override 389 public Iterator<String> iterator() { 390 return splittingIterator(sequence); 391 } 392 393 @Override 394 public String toString() { 395 return Joiner.on(", ") 396 .appendTo(new StringBuilder().append('['), this) 397 .append(']') 398 .toString(); 399 } 400 }; 401 } 402 403 private Iterator<String> splittingIterator(CharSequence sequence) { 404 return strategy.iterator(this, sequence); 405 } 406 407 /** 408 * Splits {@code sequence} into string components and returns them as an immutable list. If you 409 * want an {@link Iterable} which may be lazily evaluated, use {@link #split(CharSequence)}. 410 * 411 * @param sequence the sequence of characters to split 412 * @return an immutable list of the segments split from the parameter 413 * @since 15.0 414 */ 415 public List<String> splitToList(CharSequence sequence) { 416 checkNotNull(sequence); 417 418 Iterator<String> iterator = splittingIterator(sequence); 419 List<String> result = new ArrayList<>(); 420 421 while (iterator.hasNext()) { 422 result.add(iterator.next()); 423 } 424 425 return Collections.unmodifiableList(result); 426 } 427 428 /** 429 * Splits {@code sequence} into string components and makes them available through an {@link 430 * Stream}, which may be lazily evaluated. If you want an eagerly computed {@link List}, use 431 * {@link #splitToList(CharSequence)}. 432 * 433 * @param sequence the sequence of characters to split 434 * @return a stream over the segments split from the parameter 435 * @since 28.2 436 */ 437 public Stream<String> splitToStream(CharSequence sequence) { 438 // Can't use Streams.stream() from base 439 return StreamSupport.stream(split(sequence).spliterator(), false); 440 } 441 442 /** 443 * Returns a {@code MapSplitter} which splits entries based on this splitter, and splits entries 444 * into keys and values using the specified separator. 445 * 446 * @since 10.0 447 */ 448 public MapSplitter withKeyValueSeparator(String separator) { 449 return withKeyValueSeparator(on(separator)); 450 } 451 452 /** 453 * Returns a {@code MapSplitter} which splits entries based on this splitter, and splits entries 454 * into keys and values using the specified separator. 455 * 456 * @since 14.0 457 */ 458 public MapSplitter withKeyValueSeparator(char separator) { 459 return withKeyValueSeparator(on(separator)); 460 } 461 462 /** 463 * Returns a {@code MapSplitter} which splits entries based on this splitter, and splits entries 464 * into keys and values using the specified key-value splitter. 465 * 466 * <p>Note: Any configuration option configured on this splitter, such as {@link #trimResults}, 467 * does not change the behavior of the {@code keyValueSplitter}. 468 * 469 * <p>Example: 470 * 471 * <pre>{@code 472 * String toSplit = " x -> y, z-> a "; 473 * Splitter outerSplitter = Splitter.on(',').trimResults(); 474 * MapSplitter mapSplitter = outerSplitter.withKeyValueSeparator(Splitter.on("->")); 475 * Map<String, String> result = mapSplitter.split(toSplit); 476 * assertThat(result).isEqualTo(ImmutableMap.of("x ", " y", "z", " a")); 477 * }</pre> 478 * 479 * @since 10.0 480 */ 481 public MapSplitter withKeyValueSeparator(Splitter keyValueSplitter) { 482 return new MapSplitter(this, keyValueSplitter); 483 } 484 485 /** 486 * An object that splits strings into maps as {@code Splitter} splits iterables and lists. Like 487 * {@code Splitter}, it is thread-safe and immutable. The common way to build instances is by 488 * providing an additional {@linkplain Splitter#withKeyValueSeparator key-value separator} to 489 * {@link Splitter}. 490 * 491 * @since 10.0 492 */ 493 public static final class MapSplitter { 494 private static final String INVALID_ENTRY_MESSAGE = "Chunk [%s] is not a valid entry"; 495 private final Splitter outerSplitter; 496 private final Splitter entrySplitter; 497 498 private MapSplitter(Splitter outerSplitter, Splitter entrySplitter) { 499 this.outerSplitter = outerSplitter; // only "this" is passed 500 this.entrySplitter = checkNotNull(entrySplitter); 501 } 502 503 /** 504 * Splits {@code sequence} into substrings, splits each substring into an entry, and returns an 505 * unmodifiable map with each of the entries. For example, {@code 506 * Splitter.on(';').trimResults().withKeyValueSeparator("=>").split("a=>b ; c=>b")} will return 507 * a mapping from {@code "a"} to {@code "b"} and {@code "c"} to {@code "b"}. 508 * 509 * <p>The returned map preserves the order of the entries from {@code sequence}. 510 * 511 * @throws IllegalArgumentException if the specified sequence does not split into valid map 512 * entries, or if there are duplicate keys 513 */ 514 public Map<String, String> split(CharSequence sequence) { 515 Map<String, String> map = new LinkedHashMap<>(); 516 for (String entry : outerSplitter.split(sequence)) { 517 Iterator<String> entryFields = entrySplitter.splittingIterator(entry); 518 519 checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); 520 String key = entryFields.next(); 521 checkArgument(!map.containsKey(key), "Duplicate key [%s] found.", key); 522 523 checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); 524 String value = entryFields.next(); 525 map.put(key, value); 526 527 checkArgument(!entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); 528 } 529 return Collections.unmodifiableMap(map); 530 } 531 } 532 533 private interface Strategy { 534 Iterator<String> iterator(Splitter splitter, CharSequence toSplit); 535 } 536 537 private abstract static class SplittingIterator extends AbstractIterator<String> { 538 final CharSequence toSplit; 539 final CharMatcher trimmer; 540 final boolean omitEmptyStrings; 541 542 /** 543 * Returns the first index in {@code toSplit} at or after {@code start} that contains the 544 * separator. 545 */ 546 abstract int separatorStart(int start); 547 548 /** 549 * Returns the first index in {@code toSplit} after {@code separatorPosition} that does not 550 * contain a separator. This method is only invoked after a call to {@code separatorStart}. 551 */ 552 abstract int separatorEnd(int separatorPosition); 553 554 int offset = 0; 555 int limit; 556 557 protected SplittingIterator(Splitter splitter, CharSequence toSplit) { 558 this.trimmer = splitter.trimmer; 559 this.omitEmptyStrings = splitter.omitEmptyStrings; 560 this.limit = splitter.limit; 561 this.toSplit = toSplit; 562 } 563 564 @CheckForNull 565 @Override 566 protected String computeNext() { 567 /* 568 * The returned string will be from the end of the last match to the beginning of the next 569 * one. nextStart is the start position of the returned substring, while offset is the place 570 * to start looking for a separator. 571 */ 572 int nextStart = offset; 573 while (offset != -1) { 574 int start = nextStart; 575 int end; 576 577 int separatorPosition = separatorStart(offset); 578 if (separatorPosition == -1) { 579 end = toSplit.length(); 580 offset = -1; 581 } else { 582 end = separatorPosition; 583 offset = separatorEnd(separatorPosition); 584 } 585 if (offset == nextStart) { 586 /* 587 * This occurs when some pattern has an empty match, even if it doesn't match the empty 588 * string -- for example, if it requires lookahead or the like. The offset must be 589 * increased to look for separators beyond this point, without changing the start position 590 * of the next returned substring -- so nextStart stays the same. 591 */ 592 offset++; 593 if (offset > toSplit.length()) { 594 offset = -1; 595 } 596 continue; 597 } 598 599 while (start < end && trimmer.matches(toSplit.charAt(start))) { 600 start++; 601 } 602 while (end > start && trimmer.matches(toSplit.charAt(end - 1))) { 603 end--; 604 } 605 606 if (omitEmptyStrings && start == end) { 607 // Don't include the (unused) separator in next split string. 608 nextStart = offset; 609 continue; 610 } 611 612 if (limit == 1) { 613 // The limit has been reached, return the rest of the string as the 614 // final item. This is tested after empty string removal so that 615 // empty strings do not count towards the limit. 616 end = toSplit.length(); 617 offset = -1; 618 // Since we may have changed the end, we need to trim it again. 619 while (end > start && trimmer.matches(toSplit.charAt(end - 1))) { 620 end--; 621 } 622 } else { 623 limit--; 624 } 625 626 return toSplit.subSequence(start, end).toString(); 627 } 628 return endOfData(); 629 } 630 } 631}