1 /*
2 * Copyright (c) 1994, 2004, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.util;
27
28 import java.lang.*;
29
30 /**
31 * The string tokenizer class allows an application to break a
32 * string into tokens. The tokenization method is much simpler than
33 * the one used by the {@code StreamTokenizer} class. The
34 * {@code StringTokenizer} methods do not distinguish among
35 * identifiers, numbers, and quoted strings, nor do they recognize
36 * and skip comments.
37 * <p>
38 * The set of delimiters (the characters that separate tokens) may
39 * be specified either at creation time or on a per-token basis.
40 * <p>
41 * An instance of {@code StringTokenizer} behaves in one of two
42 * ways, depending on whether it was created with the
43 * {@code returnDelims} flag having the value {@code true}
44 * or {@code false}:
45 * <ul>
46 * <li>If the flag is {@code false}, delimiter characters serve to
47 * separate tokens. A token is a maximal sequence of consecutive
48 * characters that are not delimiters.
49 * <li>If the flag is {@code true}, delimiter characters are themselves
50 * considered to be tokens. A token is thus either one delimiter
51 * character, or a maximal sequence of consecutive characters that are
52 * not delimiters.
53 * </ul><p>
54 * A {@code StringTokenizer} object internally maintains a current
55 * position within the string to be tokenized. Some operations advance this
56 * current position past the characters processed.<p>
57 * A token is returned by taking a substring of the string that was used to
58 * create the {@code StringTokenizer} object.
59 * <p>
60 * The following is one example of the use of the tokenizer. The code:
61 * <blockquote><pre>
62 * StringTokenizer st = new StringTokenizer("this is a test");
63 * while (st.hasMoreTokens()) {
64 * System.out.println(st.nextToken());
65 * }
66 * </pre></blockquote>
67 * <p>
68 * prints the following output:
69 * <blockquote><pre>
70 * this
71 * is
72 * a
73 * test
74 * </pre></blockquote>
75 *
76 * <p>
77 * {@code StringTokenizer} is a legacy class that is retained for
78 * compatibility reasons although its use is discouraged in new code. It is
79 * recommended that anyone seeking this functionality use the {@code split}
80 * method of {@code String} or the java.util.regex package instead.
81 * <p>
82 * The following example illustrates how the {@code String.split}
83 * method can be used to break up a string into its basic tokens:
84 * <blockquote><pre>
85 * String[] result = "this is a test".split("\\s");
86 * for (int x=0; x<result.length; x++)
87 * System.out.println(result[x]);
88 * </pre></blockquote>
89 * <p>
90 * prints the following output:
91 * <blockquote><pre>
92 * this
93 * is
94 * a
95 * test
96 * </pre></blockquote>
97 *
98 * @author unascribed
99 * @see java.io.StreamTokenizer
100 * @since 1.0
101 */
102 public
103 class StringTokenizer implements Enumeration<Object> {
104 private int currentPosition;
105 private int newPosition;
106 private int maxPosition;
107 private String str;
108 private String delimiters;
109 private boolean retDelims;
110 private boolean delimsChanged;
111
112 /**
113 * maxDelimCodePoint stores the value of the delimiter character with the
114 * highest value. It is used to optimize the detection of delimiter
115 * characters.
116 *
117 * It is unlikely to provide any optimization benefit in the
118 * hasSurrogates case because most string characters will be
119 * smaller than the limit, but we keep it so that the two code
120 * paths remain similar.
121 */
122 private int maxDelimCodePoint;
123
124 /**
125 * If delimiters include any surrogates (including surrogate
126 * pairs), hasSurrogates is true and the tokenizer uses the
127 * different code path. This is because String.indexOf(int)
128 * doesn't handle unpaired surrogates as a single character.
129 */
130 private boolean hasSurrogates = false;
131
132 /**
133 * When hasSurrogates is true, delimiters are converted to code
134 * points and isDelimiter(int) is used to determine if the given
135 * codepoint is a delimiter.
136 */
137 private int[] delimiterCodePoints;
138
139 /**
140 * Set maxDelimCodePoint to the highest char in the delimiter set.
141 */
142 private void setMaxDelimCodePoint() {
143 if (delimiters == null) {
144 maxDelimCodePoint = 0;
145 return;
146 }
147
148 int m = 0;
149 int c;
150 int count = 0;
151 for (int i = 0; i < delimiters.length(); i += Character.charCount(c)) {
152 c = delimiters.charAt(i);
153 if (c >= Character.MIN_HIGH_SURROGATE && c <= Character.MAX_LOW_SURROGATE) {
154 c = delimiters.codePointAt(i);
155 hasSurrogates = true;
156 }
157 if (m < c)
158 m = c;
159 count++;
160 }
161 maxDelimCodePoint = m;
162
163 if (hasSurrogates) {
164 delimiterCodePoints = new int[count];
165 for (int i = 0, j = 0; i < count; i++, j += Character.charCount(c)) {
166 c = delimiters.codePointAt(j);
167 delimiterCodePoints[i] = c;
168 }
169 }
170 }
171
172 /**
173 * Constructs a string tokenizer for the specified string. All
174 * characters in the {@code delim} argument are the delimiters
175 * for separating tokens.
176 * <p>
177 * If the {@code returnDelims} flag is {@code true}, then
178 * the delimiter characters are also returned as tokens. Each
179 * delimiter is returned as a string of length one. If the flag is
180 * {@code false}, the delimiter characters are skipped and only
181 * serve as separators between tokens.
182 * <p>
183 * Note that if {@code delim} is {@code null}, this constructor does
184 * not throw an exception. However, trying to invoke other methods on the
185 * resulting {@code StringTokenizer} may result in a
186 * {@code NullPointerException}.
187 *
188 * @param str a string to be parsed.
189 * @param delim the delimiters.
190 * @param returnDelims flag indicating whether to return the delimiters
191 * as tokens.
192 * @exception NullPointerException if str is {@code null}
193 */
194 public StringTokenizer(String str, String delim, boolean returnDelims) {
195 currentPosition = 0;
196 newPosition = -1;
197 delimsChanged = false;
198 this.str = str;
199 maxPosition = str.length();
200 delimiters = delim;
201 retDelims = returnDelims;
202 setMaxDelimCodePoint();
203 }
204
205 /**
206 * Constructs a string tokenizer for the specified string. The
207 * characters in the {@code delim} argument are the delimiters
208 * for separating tokens. Delimiter characters themselves will not
209 * be treated as tokens.
210 * <p>
211 * Note that if {@code delim} is {@code null}, this constructor does
212 * not throw an exception. However, trying to invoke other methods on the
213 * resulting {@code StringTokenizer} may result in a
214 * {@code NullPointerException}.
215 *
216 * @param str a string to be parsed.
217 * @param delim the delimiters.
218 * @exception NullPointerException if str is {@code null}
219 */
220 public StringTokenizer(String str, String delim) {
221 this(str, delim, false);
222 }
223
224 /**
225 * Constructs a string tokenizer for the specified string. The
226 * tokenizer uses the default delimiter set, which is
227 * <code>" \t\n\r\f"</code>: the space character,
228 * the tab character, the newline character, the carriage-return character,
229 * and the form-feed character. Delimiter characters themselves will
230 * not be treated as tokens.
231 *
232 * @param str a string to be parsed.
233 * @exception NullPointerException if str is {@code null}
234 */
235 public StringTokenizer(String str) {
236 this(str, " \t\n\r\f", false);
237 }
238
239 /**
240 * Skips delimiters starting from the specified position. If retDelims
241 * is false, returns the index of the first non-delimiter character at or
242 * after startPos. If retDelims is true, startPos is returned.
243 */
244 private int skipDelimiters(int startPos) {
245 if (delimiters == null)
246 throw new NullPointerException();
247
248 int position = startPos;
249 while (!retDelims && position < maxPosition) {
250 if (!hasSurrogates) {
251 char c = str.charAt(position);
252 if ((c > maxDelimCodePoint) || (delimiters.indexOf(c) < 0))
253 break;
254 position++;
255 } else {
256 int c = str.codePointAt(position);
257 if ((c > maxDelimCodePoint) || !isDelimiter(c)) {
258 break;
259 }
260 position += Character.charCount(c);
261 }
262 }
263 return position;
264 }
265
266 /**
267 * Skips ahead from startPos and returns the index of the next delimiter
268 * character encountered, or maxPosition if no such delimiter is found.
269 */
270 private int scanToken(int startPos) {
271 int position = startPos;
272 while (position < maxPosition) {
273 if (!hasSurrogates) {
274 char c = str.charAt(position);
275 if ((c <= maxDelimCodePoint) && (delimiters.indexOf(c) >= 0))
276 break;
277 position++;
278 } else {
279 int c = str.codePointAt(position);
280 if ((c <= maxDelimCodePoint) && isDelimiter(c))
281 break;
282 position += Character.charCount(c);
283 }
284 }
285 if (retDelims && (startPos == position)) {
286 if (!hasSurrogates) {
287 char c = str.charAt(position);
288 if ((c <= maxDelimCodePoint) && (delimiters.indexOf(c) >= 0))
289 position++;
290 } else {
291 int c = str.codePointAt(position);
292 if ((c <= maxDelimCodePoint) && isDelimiter(c))
293 position += Character.charCount(c);
294 }
295 }
296 return position;
297 }
298
299 private boolean isDelimiter(int codePoint) {
300 for (int delimiterCodePoint : delimiterCodePoints) {
301 if (delimiterCodePoint == codePoint) {
302 return true;
303 }
304 }
305 return false;
306 }
307
308 /**
309 * Tests if there are more tokens available from this tokenizer's string.
310 * If this method returns {@code true}, then a subsequent call to
311 * {@code nextToken} with no argument will successfully return a token.
312 *
313 * @return {@code true} if and only if there is at least one token
314 * in the string after the current position; {@code false}
315 * otherwise.
316 */
317 public boolean hasMoreTokens() {
318 /*
319 * Temporarily store this position and use it in the following
320 * nextToken() method only if the delimiters haven't been changed in
321 * that nextToken() invocation.
322 */
323 newPosition = skipDelimiters(currentPosition);
324 return (newPosition < maxPosition);
325 }
326
327 /**
328 * Returns the next token from this string tokenizer.
329 *
330 * @return the next token from this string tokenizer.
331 * @exception NoSuchElementException if there are no more tokens in this
332 * tokenizer's string.
333 */
334 public String nextToken() {
335 /*
336 * If next position already computed in hasMoreElements() and
337 * delimiters have changed between the computation and this invocation,
338 * then use the computed value.
339 */
340
341 currentPosition = (newPosition >= 0 && !delimsChanged) ?
342 newPosition : skipDelimiters(currentPosition);
343
344 /* Reset these anyway */
345 delimsChanged = false;
346 newPosition = -1;
347
348 if (currentPosition >= maxPosition)
349 throw new NoSuchElementException();
350 int start = currentPosition;
351 currentPosition = scanToken(currentPosition);
352 return str.substring(start, currentPosition);
353 }
354
355 /**
356 * Returns the next token in this string tokenizer's string. First,
357 * the set of characters considered to be delimiters by this
358 * {@code StringTokenizer} object is changed to be the characters in
359 * the string {@code delim}. Then the next token in the string
360 * after the current position is returned. The current position is
361 * advanced beyond the recognized token. The new delimiter set
362 * remains the default after this call.
363 *
364 * @param delim the new delimiters.
365 * @return the next token, after switching to the new delimiter set.
366 * @exception NoSuchElementException if there are no more tokens in this
367 * tokenizer's string.
368 * @exception NullPointerException if delim is {@code null}
369 */
370 public String nextToken(String delim) {
371 delimiters = delim;
372
373 /* delimiter string specified, so set the appropriate flag. */
374 delimsChanged = true;
375
376 setMaxDelimCodePoint();
377 return nextToken();
378 }
379
380 /**
381 * Returns the same value as the {@code hasMoreTokens}
382 * method. It exists so that this class can implement the
383 * {@code Enumeration} interface.
384 *
385 * @return {@code true} if there are more tokens;
386 * {@code false} otherwise.
387 * @see java.util.Enumeration
388 * @see java.util.StringTokenizer#hasMoreTokens()
389 */
390 public boolean hasMoreElements() {
391 return hasMoreTokens();
392 }
393
394 /**
395 * Returns the same value as the {@code nextToken} method,
396 * except that its declared return value is {@code Object} rather than
397 * {@code String}. It exists so that this class can implement the
398 * {@code Enumeration} interface.
399 *
400 * @return the next token in the string.
401 * @exception NoSuchElementException if there are no more tokens in this
402 * tokenizer's string.
403 * @see java.util.Enumeration
404 * @see java.util.StringTokenizer#nextToken()
405 */
406 public Object nextElement() {
407 return nextToken();
408 }
409
410 /**
411 * Calculates the number of times that this tokenizer's
412 * {@code nextToken} method can be called before it generates an
413 * exception. The current position is not advanced.
414 *
415 * @return the number of tokens remaining in the string using the current
416 * delimiter set.
417 * @see java.util.StringTokenizer#nextToken()
418 */
419 public int countTokens() {
420 int count = 0;
421 int currpos = currentPosition;
422 while (currpos < maxPosition) {
423 currpos = skipDelimiters(currpos);
424 if (currpos >= maxPosition)
425 break;
426 currpos = scanToken(currpos);
427 count++;
428 }
429 return count;
430 }
431 }