1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.lang;
18
19 import java.util.Random;
20 /**
21 * <p>Operations for random <code>String</code>s.</p>
22 * <p>Currently <em>private high surrogate</em> characters are ignored.
23 * These are unicode characters that fall between the values 56192 (db80)
24 * and 56319 (dbff) as we don't know how to handle them.
25 * High and low surrogates are correctly dealt with - that is if a
26 * high surrogate is randomly chosen, 55296 (d800) to 56191 (db7f)
27 * then it is followed by a low surrogate. If a low surrogate is chosen,
28 * 56320 (dc00) to 57343 (dfff) then it is placed after a randomly
29 * chosen high surrogate. </p>
30 *
31 * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
32 * @author Stephen Colebourne
33 * @author Gary Gregory
34 * @author Phil Steitz
35 * @since 1.0
36 * @version $Id: RandomStringUtils.java 471626 2006-11-06 04:02:09Z bayard $
37 */
38 public class RandomStringUtils {
39
40 /**
41 * <p>Random object used by random method. This has to be not local
42 * to the random method so as to not return the same value in the
43 * same millisecond.</p>
44 */
45 private static final Random RANDOM = new Random();
46
47 /**
48 * <p><code>RandomStringUtils</code> instances should NOT be constructed in
49 * standard programming. Instead, the class should be used as
50 * <code>RandomStringUtils.random(5);</code>.</p>
51 *
52 * <p>This constructor is public to permit tools that require a JavaBean instance
53 * to operate.</p>
54 */
55 public RandomStringUtils() {
56 super();
57 }
58
59 // Random
60 //-----------------------------------------------------------------------
61 /**
62 * <p>Creates a random string whose length is the number of characters
63 * specified.</p>
64 *
65 * <p>Characters will be chosen from the set of all characters.</p>
66 *
67 * @param count the length of random string to create
68 * @return the random string
69 */
70 public static String random(int count) {
71 return random(count, false, false);
72 }
73
74 /**
75 * <p>Creates a random string whose length is the number of characters
76 * specified.</p>
77 *
78 * <p>Characters will be chosen from the set of characters whose
79 * ASCII value is between <code>32</code> and <code>126</code> (inclusive).</p>
80 *
81 * @param count the length of random string to create
82 * @return the random string
83 */
84 public static String randomAscii(int count) {
85 return random(count, 32, 127, false, false);
86 }
87
88 /**
89 * <p>Creates a random string whose length is the number of characters
90 * specified.</p>
91 *
92 * <p>Characters will be chosen from the set of alphabetic
93 * characters.</p>
94 *
95 * @param count the length of random string to create
96 * @return the random string
97 */
98 public static String randomAlphabetic(int count) {
99 return random(count, true, false);
100 }
101
102 /**
103 * <p>Creates a random string whose length is the number of characters
104 * specified.</p>
105 *
106 * <p>Characters will be chosen from the set of alpha-numeric
107 * characters.</p>
108 *
109 * @param count the length of random string to create
110 * @return the random string
111 */
112 public static String randomAlphanumeric(int count) {
113 return random(count, true, true);
114 }
115
116 /**
117 * <p>Creates a random string whose length is the number of characters
118 * specified.</p>
119 *
120 * <p>Characters will be chosen from the set of numeric
121 * characters.</p>
122 *
123 * @param count the length of random string to create
124 * @return the random string
125 */
126 public static String randomNumeric(int count) {
127 return random(count, false, true);
128 }
129
130 /**
131 * <p>Creates a random string whose length is the number of characters
132 * specified.</p>
133 *
134 * <p>Characters will be chosen from the set of alpha-numeric
135 * characters as indicated by the arguments.</p>
136 *
137 * @param count the length of random string to create
138 * @param letters if <code>true</code>, generated string will include
139 * alphabetic characters
140 * @param numbers if <code>true</code>, generated string will include
141 * numeric characters
142 * @return the random string
143 */
144 public static String random(int count, boolean letters, boolean numbers) {
145 return random(count, 0, 0, letters, numbers);
146 }
147
148 /**
149 * <p>Creates a random string whose length is the number of characters
150 * specified.</p>
151 *
152 * <p>Characters will be chosen from the set of alpha-numeric
153 * characters as indicated by the arguments.</p>
154 *
155 * @param count the length of random string to create
156 * @param start the position in set of chars to start at
157 * @param end the position in set of chars to end before
158 * @param letters if <code>true</code>, generated string will include
159 * alphabetic characters
160 * @param numbers if <code>true</code>, generated string will include
161 * numeric characters
162 * @return the random string
163 */
164 public static String random(int count, int start, int end, boolean letters, boolean numbers) {
165 return random(count, start, end, letters, numbers, null, RANDOM);
166 }
167
168 /**
169 * <p>Creates a random string based on a variety of options, using
170 * default source of randomness.</p>
171 *
172 * <p>This method has exactly the same semantics as
173 * {@link #random(int,int,int,boolean,boolean,char[],Random)}, but
174 * instead of using an externally supplied source of randomness, it uses
175 * the internal static {@link Random} instance.</p>
176 *
177 * @param count the length of random string to create
178 * @param start the position in set of chars to start at
179 * @param end the position in set of chars to end before
180 * @param letters only allow letters?
181 * @param numbers only allow numbers?
182 * @param chars the set of chars to choose randoms from.
183 * If <code>null</code>, then it will use the set of all chars.
184 * @return the random string
185 * @throws ArrayIndexOutOfBoundsException if there are not
186 * <code>(end - start) + 1</code> characters in the set array.
187 */
188 public static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars) {
189 return random(count, start, end, letters, numbers, chars, RANDOM);
190 }
191
192 /**
193 * <p>Creates a random string based on a variety of options, using
194 * supplied source of randomness.</p>
195 *
196 * <p>If start and end are both <code>0</code>, start and end are set
197 * to <code>' '</code> and <code>'z'</code>, the ASCII printable
198 * characters, will be used, unless letters and numbers are both
199 * <code>false</code>, in which case, start and end are set to
200 * <code>0</code> and <code>Integer.MAX_VALUE</code>.
201 *
202 * <p>If set is not <code>null</code>, characters between start and
203 * end are chosen.</p>
204 *
205 * <p>This method accepts a user-supplied {@link Random}
206 * instance to use as a source of randomness. By seeding a single
207 * {@link Random} instance with a fixed seed and using it for each call,
208 * the same random sequence of strings can be generated repeatedly
209 * and predictably.</p>
210 *
211 * @param count the length of random string to create
212 * @param start the position in set of chars to start at
213 * @param end the position in set of chars to end before
214 * @param letters only allow letters?
215 * @param numbers only allow numbers?
216 * @param chars the set of chars to choose randoms from.
217 * If <code>null</code>, then it will use the set of all chars.
218 * @param random a source of randomness.
219 * @return the random string
220 * @throws ArrayIndexOutOfBoundsException if there are not
221 * <code>(end - start) + 1</code> characters in the set array.
222 * @throws IllegalArgumentException if <code>count</code> < 0.
223 * @since 2.0
224 */
225 public static String random(int count, int start, int end, boolean letters, boolean numbers,
226 char[] chars, Random random) {
227 if (count == 0) {
228 return "";
229 } else if (count < 0) {
230 throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
231 }
232 if ((start == 0) && (end == 0)) {
233 end = 'z' + 1;
234 start = ' ';
235 if (!letters && !numbers) {
236 start = 0;
237 end = Integer.MAX_VALUE;
238 }
239 }
240
241 char[] buffer = new char[count];
242 int gap = end - start;
243
244 while (count-- != 0) {
245 char ch;
246 if (chars == null) {
247 ch = (char) (random.nextInt(gap) + start);
248 } else {
249 ch = chars[random.nextInt(gap) + start];
250 }
251 if ((letters && Character.isLetter(ch))
252 || (numbers && Character.isDigit(ch))
253 || (!letters && !numbers))
254 {
255 if(ch >= 56320 && ch <= 57343) {
256 if(count == 0) {
257 count++;
258 } else {
259 // low surrogate, insert high surrogate after putting it in
260 buffer[count] = ch;
261 count--;
262 buffer[count] = (char) (55296 + random.nextInt(128));
263 }
264 } else if(ch >= 55296 && ch <= 56191) {
265 if(count == 0) {
266 count++;
267 } else {
268 // high surrogate, insert low surrogate before putting it in
269 buffer[count] = (char) (56320 + random.nextInt(128));
270 count--;
271 buffer[count] = ch;
272 }
273 } else if(ch >= 56192 && ch <= 56319) {
274 // private high surrogate, no effing clue, so skip it
275 count++;
276 } else {
277 buffer[count] = ch;
278 }
279 } else {
280 count++;
281 }
282 }
283 return new String(buffer);
284 }
285
286 /**
287 * <p>Creates a random string whose length is the number of characters
288 * specified.</p>
289 *
290 * <p>Characters will be chosen from the set of characters
291 * specified.</p>
292 *
293 * @param count the length of random string to create
294 * @param chars the String containing the set of characters to use,
295 * may be null
296 * @return the random string
297 * @throws IllegalArgumentException if <code>count</code> < 0.
298 */
299 public static String random(int count, String chars) {
300 if (chars == null) {
301 return random(count, 0, 0, false, false, null, RANDOM);
302 }
303 return random(count, chars.toCharArray());
304 }
305
306 /**
307 * <p>Creates a random string whose length is the number of characters
308 * specified.</p>
309 *
310 * <p>Characters will be chosen from the set of characters specified.</p>
311 *
312 * @param count the length of random string to create
313 * @param chars the character array containing the set of characters to use,
314 * may be null
315 * @return the random string
316 * @throws IllegalArgumentException if <code>count</code> < 0.
317 */
318 public static String random(int count, char[] chars) {
319 if (chars == null) {
320 return random(count, 0, 0, false, false, null, RANDOM);
321 }
322 return random(count, 0, chars.length, false, false, chars, RANDOM);
323 }
324
325 }