001 /*
002 * Copyright (C) 2009 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
017 package com.google.common.base;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkNotNull;
021
022 import com.google.common.annotations.Beta;
023 import com.google.common.annotations.GwtCompatible;
024 import com.google.common.annotations.GwtIncompatible;
025
026 import java.util.Collections;
027 import java.util.Iterator;
028 import java.util.LinkedHashMap;
029 import java.util.Map;
030 import java.util.regex.Matcher;
031 import java.util.regex.Pattern;
032
033 import javax.annotation.CheckReturnValue;
034
035 /**
036 * An object that divides strings (or other instances of {@code CharSequence})
037 * into substrings, by recognizing a <i>separator</i> (a.k.a. "delimiter")
038 * which can be expressed as a single character, literal string, regular
039 * expression, {@code CharMatcher}, or by using a fixed substring length. This
040 * class provides the complementary functionality to {@link Joiner}.
041 *
042 * <p>Here is the most basic example of {@code Splitter} usage: <pre> {@code
043 *
044 * Splitter.on(',').split("foo,bar")}</pre>
045 *
046 * This invocation returns an {@code Iterable<String>} containing {@code "foo"}
047 * and {@code "bar"}, in that order.
048 *
049 * <p>By default {@code Splitter}'s behavior is very simplistic: <pre> {@code
050 *
051 * Splitter.on(',').split("foo,,bar, quux")}</pre>
052 *
053 * This returns an iterable containing {@code ["foo", "", "bar", " quux"]}.
054 * Notice that the splitter does not assume that you want empty strings removed,
055 * or that you wish to trim whitespace. If you want features like these, simply
056 * ask for them: <pre> {@code
057 *
058 * private static final Splitter MY_SPLITTER = Splitter.on(',')
059 * .trimResults()
060 * .omitEmptyStrings();}</pre>
061 *
062 * Now {@code MY_SPLITTER.split("foo, ,bar, quux,")} returns an iterable
063 * containing just {@code ["foo", "bar", "quux"]}. Note that the order in which
064 * the configuration methods are called is never significant; for instance,
065 * trimming is always applied first before checking for an empty result,
066 * regardless of the order in which the {@link #trimResults()} and
067 * {@link #omitEmptyStrings()} methods were invoked.
068 *
069 * <p><b>Warning: splitter instances are always immutable</b>; a configuration
070 * method such as {@code omitEmptyStrings} has no effect on the instance it
071 * is invoked on! You must store and use the new splitter instance returned by
072 * the method. This makes splitters thread-safe, and safe to store as {@code
073 * static final} constants (as illustrated above). <pre> {@code
074 *
075 * // Bad! Do not do this!
076 * Splitter splitter = Splitter.on('/');
077 * splitter.trimResults(); // does nothing!
078 * return splitter.split("wrong / wrong / wrong");}</pre>
079 *
080 * The separator recognized by the splitter does not have to be a single
081 * literal character as in the examples above. See the methods {@link
082 * #on(String)}, {@link #on(Pattern)} and {@link #on(CharMatcher)} for examples
083 * of other ways to specify separators.
084 *
085 * <p><b>Note:</b> this class does not mimic any of the quirky behaviors of
086 * similar JDK methods; for instance, it does not silently discard trailing
087 * separators, as does {@link String#split(String)}, nor does it have a default
088 * behavior of using five particular whitespace characters as separators, like
089 * {@link java.util.StringTokenizer}.
090 *
091 * @author Julien Silland
092 * @author Jesse Wilson
093 * @author Kevin Bourrillion
094 * @author Louis Wasserman
095 * @since 1.0
096 */
097 @GwtCompatible(emulated = true)
098 public final class Splitter {
099 private final CharMatcher trimmer;
100 private final boolean omitEmptyStrings;
101 private final Strategy strategy;
102 private final int limit;
103
104 private Splitter(Strategy strategy) {
105 this(strategy, false, CharMatcher.NONE, Integer.MAX_VALUE);
106 }
107
108 private Splitter(Strategy strategy, boolean omitEmptyStrings,
109 CharMatcher trimmer, int limit) {
110 this.strategy = strategy;
111 this.omitEmptyStrings = omitEmptyStrings;
112 this.trimmer = trimmer;
113 this.limit = limit;
114 }
115
116 /**
117 * Returns a splitter that uses the given single-character separator. For
118 * example, {@code Splitter.on(',').split("foo,,bar")} returns an iterable
119 * containing {@code ["foo", "", "bar"]}.
120 *
121 * @param separator the character to recognize as a separator
122 * @return a splitter, with default settings, that recognizes that separator
123 */
124 public static Splitter on(char separator) {
125 return on(CharMatcher.is(separator));
126 }
127
128 /**
129 * Returns a splitter that considers any single character matched by the
130 * given {@code CharMatcher} to be a separator. For example, {@code
131 * Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux")} returns an
132 * iterable containing {@code ["foo", "", "bar", "quux"]}.
133 *
134 * @param separatorMatcher a {@link CharMatcher} that determines whether a
135 * character is a separator
136 * @return a splitter, with default settings, that uses this matcher
137 */
138 public static Splitter on(final CharMatcher separatorMatcher) {
139 checkNotNull(separatorMatcher);
140
141 return new Splitter(new Strategy() {
142 @Override public SplittingIterator iterator(
143 Splitter splitter, final CharSequence toSplit) {
144 return new SplittingIterator(splitter, toSplit) {
145 @Override int separatorStart(int start) {
146 return separatorMatcher.indexIn(toSplit, start);
147 }
148
149 @Override int separatorEnd(int separatorPosition) {
150 return separatorPosition + 1;
151 }
152 };
153 }
154 });
155 }
156
157 /**
158 * Returns a splitter that uses the given fixed string as a separator. For
159 * example, {@code Splitter.on(", ").split("foo, bar, baz,qux")} returns an
160 * iterable containing {@code ["foo", "bar", "baz,qux"]}.
161 *
162 * @param separator the literal, nonempty string to recognize as a separator
163 * @return a splitter, with default settings, that recognizes that separator
164 */
165 public static Splitter on(final String separator) {
166 checkArgument(separator.length() != 0,
167 "The separator may not be the empty string.");
168
169 return new Splitter(new Strategy() {
170 @Override public SplittingIterator iterator(
171 Splitter splitter, CharSequence toSplit) {
172 return new SplittingIterator(splitter, toSplit) {
173 @Override public int separatorStart(int start) {
174 int delimeterLength = separator.length();
175
176 positions:
177 for (int p = start, last = toSplit.length() - delimeterLength;
178 p <= last; p++) {
179 for (int i = 0; i < delimeterLength; i++) {
180 if (toSplit.charAt(i + p) != separator.charAt(i)) {
181 continue positions;
182 }
183 }
184 return p;
185 }
186 return -1;
187 }
188
189 @Override public int separatorEnd(int separatorPosition) {
190 return separatorPosition + separator.length();
191 }
192 };
193 }
194 });
195 }
196
197 /**
198 * Returns a splitter that considers any subsequence matching {@code
199 * pattern} to be a separator. For example, {@code
200 * Splitter.on(Pattern.compile("\r?\n")).split(entireFile)} splits a string
201 * into lines whether it uses DOS-style or UNIX-style line terminators.
202 *
203 * @param separatorPattern the pattern that determines whether a subsequence
204 * is a separator. This pattern may not match the empty string.
205 * @return a splitter, with default settings, that uses this pattern
206 * @throws IllegalArgumentException if {@code separatorPattern} matches the
207 * empty string
208 */
209 @GwtIncompatible("java.util.regex")
210 public static Splitter on(final Pattern separatorPattern) {
211 checkNotNull(separatorPattern);
212 checkArgument(!separatorPattern.matcher("").matches(),
213 "The pattern may not match the empty string: %s", separatorPattern);
214
215 return new Splitter(new Strategy() {
216 @Override public SplittingIterator iterator(
217 final Splitter splitter, CharSequence toSplit) {
218 final Matcher matcher = separatorPattern.matcher(toSplit);
219 return new SplittingIterator(splitter, toSplit) {
220 @Override public int separatorStart(int start) {
221 return matcher.find(start) ? matcher.start() : -1;
222 }
223
224 @Override public int separatorEnd(int separatorPosition) {
225 return matcher.end();
226 }
227 };
228 }
229 });
230 }
231
232 /**
233 * Returns a splitter that considers any subsequence matching a given
234 * pattern (regular expression) to be a separator. For example, {@code
235 * Splitter.onPattern("\r?\n").split(entireFile)} splits a string into lines
236 * whether it uses DOS-style or UNIX-style line terminators. This is
237 * equivalent to {@code Splitter.on(Pattern.compile(pattern))}.
238 *
239 * @param separatorPattern the pattern that determines whether a subsequence
240 * is a separator. This pattern may not match the empty string.
241 * @return a splitter, with default settings, that uses this pattern
242 * @throws java.util.regex.PatternSyntaxException if {@code separatorPattern}
243 * is a malformed expression
244 * @throws IllegalArgumentException if {@code separatorPattern} matches the
245 * empty string
246 */
247 @GwtIncompatible("java.util.regex")
248 public static Splitter onPattern(String separatorPattern) {
249 return on(Pattern.compile(separatorPattern));
250 }
251
252 /**
253 * Returns a splitter that divides strings into pieces of the given length.
254 * For example, {@code Splitter.fixedLength(2).split("abcde")} returns an
255 * iterable containing {@code ["ab", "cd", "e"]}. The last piece can be
256 * smaller than {@code length} but will never be empty.
257 *
258 * @param length the desired length of pieces after splitting
259 * @return a splitter, with default settings, that can split into fixed sized
260 * pieces
261 */
262 public static Splitter fixedLength(final int length) {
263 checkArgument(length > 0, "The length may not be less than 1");
264
265 return new Splitter(new Strategy() {
266 @Override public SplittingIterator iterator(
267 final Splitter splitter, CharSequence toSplit) {
268 return new SplittingIterator(splitter, toSplit) {
269 @Override public int separatorStart(int start) {
270 int nextChunkStart = start + length;
271 return (nextChunkStart < toSplit.length() ? nextChunkStart : -1);
272 }
273
274 @Override public int separatorEnd(int separatorPosition) {
275 return separatorPosition;
276 }
277 };
278 }
279 });
280 }
281
282 /**
283 * Returns a splitter that behaves equivalently to {@code this} splitter, but
284 * automatically omits empty strings from the results. For example, {@code
285 * Splitter.on(',').omitEmptyStrings().split(",a,,,b,c,,")} returns an
286 * iterable containing only {@code ["a", "b", "c"]}.
287 *
288 * <p>If either {@code trimResults} option is also specified when creating a
289 * splitter, that splitter always trims results first before checking for
290 * emptiness. So, for example, {@code
291 * Splitter.on(':').omitEmptyStrings().trimResults().split(": : : ")} returns
292 * an empty iterable.
293 *
294 * <p>Note that it is ordinarily not possible for {@link #split(CharSequence)}
295 * to return an empty iterable, but when using this option, it can (if the
296 * input sequence consists of nothing but separators).
297 *
298 * @return a splitter with the desired configuration
299 */
300 @CheckReturnValue
301 public Splitter omitEmptyStrings() {
302 return new Splitter(strategy, true, trimmer, limit);
303 }
304
305 /**
306 * Returns a splitter that behaves equivalently to {@code this} splitter but
307 * stops splitting after it reaches the limit.
308 * The limit defines the maximum number of items returned by the iterator.
309 *
310 * <p>For example,
311 * {@code Splitter.on(',').limit(3).split("a,b,c,d")} returns an iterable
312 * containing {@code ["a", "b", "c,d"]}. When omitting empty strings, the
313 * omitted strings do no count. Hence,
314 * {@code Splitter.on(',').limit(3).omitEmptyStrings().split("a,,,b,,,c,d")}
315 * returns an iterable containing {@code ["a", "b", "c,d"}.
316 * When trim is requested, all entries, including the last are trimmed. Hence
317 * {@code Splitter.on(',').limit(3).trimResults().split(" a , b , c , d ")}
318 * results in @{code ["a", "b", "c , d"]}.
319 *
320 * @param limit the maximum number of items returns
321 * @return a splitter with the desired configuration
322 * @since 9.0
323 */
324 @CheckReturnValue
325 public Splitter limit(int limit) {
326 checkArgument(limit > 0, "must be greater than zero: %s", limit);
327 return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
328 }
329
330 /**
331 * Returns a splitter that behaves equivalently to {@code this} splitter, but
332 * automatically removes leading and trailing {@linkplain
333 * CharMatcher#WHITESPACE whitespace} from each returned substring; equivalent
334 * to {@code trimResults(CharMatcher.WHITESPACE)}. For example, {@code
335 * Splitter.on(',').trimResults().split(" a, b ,c ")} returns an iterable
336 * containing {@code ["a", "b", "c"]}.
337 *
338 * @return a splitter with the desired configuration
339 */
340 @CheckReturnValue
341 public Splitter trimResults() {
342 return trimResults(CharMatcher.WHITESPACE);
343 }
344
345 /**
346 * Returns a splitter that behaves equivalently to {@code this} splitter, but
347 * removes all leading or trailing characters matching the given {@code
348 * CharMatcher} from each returned substring. For example, {@code
349 * Splitter.on(',').trimResults(CharMatcher.is('_')).split("_a ,_b_ ,c__")}
350 * returns an iterable containing {@code ["a ", "b_ ", "c"]}.
351 *
352 * @param trimmer a {@link CharMatcher} that determines whether a character
353 * should be removed from the beginning/end of a subsequence
354 * @return a splitter with the desired configuration
355 */
356 // TODO(kevinb): throw if a trimmer was already specified!
357 @CheckReturnValue
358 public Splitter trimResults(CharMatcher trimmer) {
359 checkNotNull(trimmer);
360 return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
361 }
362
363 /**
364 * Splits {@code sequence} into string components and makes them available
365 * through an {@link Iterator}, which may be lazily evaluated.
366 *
367 * @param sequence the sequence of characters to split
368 * @return an iteration over the segments split from the parameter.
369 */
370 public Iterable<String> split(final CharSequence sequence) {
371 checkNotNull(sequence);
372
373 return new Iterable<String>() {
374 @Override public Iterator<String> iterator() {
375 return spliterator(sequence);
376 }
377 };
378 }
379
380 private Iterator<String> spliterator(CharSequence sequence) {
381 return strategy.iterator(this, sequence);
382 }
383
384 /**
385 * Returns a {@code MapSplitter} which splits entries based on this splitter,
386 * and splits entries into keys and values using the specified separator.
387 *
388 * @since 10.0
389 */
390 @CheckReturnValue
391 @Beta
392 public MapSplitter withKeyValueSeparator(String separator) {
393 return withKeyValueSeparator(on(separator));
394 }
395
396 /**
397 * Returns a {@code MapSplitter} which splits entries based on this splitter,
398 * and splits entries into keys and values using the specified key-value
399 * splitter.
400 *
401 * @since 10.0
402 */
403 @CheckReturnValue
404 @Beta
405 public MapSplitter withKeyValueSeparator(Splitter keyValueSplitter) {
406 return new MapSplitter(this, keyValueSplitter);
407 }
408
409 /**
410 * An object that splits strings into maps as {@code Splitter} splits
411 * iterables and lists. Like {@code Splitter}, it is thread-safe and
412 * immutable.
413 *
414 * @since 10.0
415 */
416 @Beta
417 public static final class MapSplitter {
418 private static final String INVALID_ENTRY_MESSAGE =
419 "Chunk [%s] is not a valid entry";
420 private final Splitter outerSplitter;
421 private final Splitter entrySplitter;
422
423 private MapSplitter(Splitter outerSplitter, Splitter entrySplitter) {
424 this.outerSplitter = outerSplitter; // only "this" is passed
425 this.entrySplitter = checkNotNull(entrySplitter);
426 }
427
428 /**
429 * Splits {@code sequence} into substrings, splits each substring into
430 * an entry, and returns an unmodifiable map with each of the entries. For
431 * example, <code>
432 * Splitter.on(';').trimResults().withKeyValueSeparator("=>")
433 * .split("a=>b ; c=>b")
434 * </code> will return a mapping from {@code "a"} to {@code "b"} and
435 * {@code "c"} to {@code b}.
436 *
437 * <p>The returned map preserves the order of the entries from
438 * {@code sequence}.
439 *
440 * @throws IllegalArgumentException if the specified sequence does not split
441 * into valid map entries, or if there are duplicate keys
442 */
443 public Map<String, String> split(CharSequence sequence) {
444 Map<String, String> map = new LinkedHashMap<String, String>();
445 for (String entry : outerSplitter.split(sequence)) {
446 Iterator<String> entryFields = entrySplitter.spliterator(entry);
447
448 checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
449 String key = entryFields.next();
450 checkArgument(!map.containsKey(key), "Duplicate key [%s] found.", key);
451
452 checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
453 String value = entryFields.next();
454 map.put(key, value);
455
456 checkArgument(!entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
457 }
458 return Collections.unmodifiableMap(map);
459 }
460 }
461
462 private interface Strategy {
463 Iterator<String> iterator(Splitter splitter, CharSequence toSplit);
464 }
465
466 private abstract static class SplittingIterator
467 extends AbstractIterator<String> {
468 final CharSequence toSplit;
469 final CharMatcher trimmer;
470 final boolean omitEmptyStrings;
471
472 /**
473 * Returns the first index in {@code toSplit} at or after {@code start}
474 * that contains the separator.
475 */
476 abstract int separatorStart(int start);
477
478 /**
479 * Returns the first index in {@code toSplit} after {@code
480 * separatorPosition} that does not contain a separator. This method is only
481 * invoked after a call to {@code separatorStart}.
482 */
483 abstract int separatorEnd(int separatorPosition);
484
485 int offset = 0;
486 int limit;
487
488 protected SplittingIterator(Splitter splitter, CharSequence toSplit) {
489 this.trimmer = splitter.trimmer;
490 this.omitEmptyStrings = splitter.omitEmptyStrings;
491 this.limit = splitter.limit;
492 this.toSplit = toSplit;
493 }
494
495 @Override protected String computeNext() {
496 while (offset != -1) {
497 int start = offset;
498 int end;
499
500 int separatorPosition = separatorStart(offset);
501 if (separatorPosition == -1) {
502 end = toSplit.length();
503 offset = -1;
504 } else {
505 end = separatorPosition;
506 offset = separatorEnd(separatorPosition);
507 }
508
509 while (start < end && trimmer.matches(toSplit.charAt(start))) {
510 start++;
511 }
512 while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
513 end--;
514 }
515
516 if (omitEmptyStrings && start == end) {
517 continue;
518 }
519
520 if (limit == 1) {
521 // The limit has been reached, return the rest of the string as the
522 // final item. This is tested after empty string removal so that
523 // empty strings do not count towards the limit.
524 end = toSplit.length();
525 offset = -1;
526 // Since we may have changed the end, we need to trim it again.
527 while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
528 end--;
529 }
530 } else {
531 limit--;
532 }
533
534 return toSplit.subSequence(start, end).toString();
535 }
536 return endOfData();
537 }
538 }
539 }