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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.lang3;
18  
19  import java.security.SecureRandom;
20  import java.security.Security;
21  import java.util.Random;
22  import java.util.concurrent.ThreadLocalRandom;
23  import java.util.function.Supplier;
24  
25  /**
26   * Generates random {@link String}s.
27   * <p>
28   * Use {@link #secure()} to get the singleton instance based on {@link SecureRandom#SecureRandom()} which uses a secure random number generator implementing the
29   * default random number algorithm.
30   * </p>
31   * <p>
32   * Use {@link #secureStrong()} to get the singleton instance based on {@link SecureRandom#getInstanceStrong()} which uses an instance that was selected by using
33   * the algorithms/providers specified in the {@code securerandom.strongAlgorithms} {@link Security} property.
34   * </p>
35   * <p>
36   * Use {@link #insecure()} to get the singleton instance based on {@link ThreadLocalRandom#current()} <b>which is not cryptographically secure</b>. In addition,
37   * instances do not use a cryptographically random seed unless the {@linkplain System#getProperty system property} {@code java.util.secureRandomSeed} is set to
38   * {@code true}.
39   * </p>
40   * <p>
41   * Starting in version 3.17.0, the method {@link #secure()} uses {@link SecureRandom#SecureRandom()} instead of {@link SecureRandom#getInstanceStrong()}, and
42   * adds {@link #secureStrong()}.
43   * </p>
44   * <p>
45   * Starting in version 3.16.0, this class uses {@link #secure()} for static methods and adds {@link #insecure()}.
46   * </p>
47   * <p>
48   * Starting in version 3.15.0, this class uses {@link SecureRandom#getInstanceStrong()} for static methods.
49   * </p>
50   * <p>
51   * Before version 3.15.0, this class used {@link ThreadLocalRandom#current()} for static methods, which is not cryptographically secure.
52   * </p>
53   * <p>
54   * RandomStringUtils is intended for simple use cases. For more advanced use cases consider using Apache Commons Text's
55   * <a href= "https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/RandomStringGenerator.html"> RandomStringGenerator</a>
56   * instead.
57   * </p>
58   * <p>
59   * The Apache Commons project provides <a href="https://commons.apache.org/proper/commons-rng/">Commons RNG</a> dedicated to pseudo-random number generation,
60   * that may be a better choice for applications with more stringent requirements (performance and/or correctness).
61   * </p>
62   * <p>
63   * Note that <em>private high surrogate</em> characters are ignored. These are Unicode characters that fall between the values 56192 (db80) and 56319 (dbff) as
64   * we don't know how to handle them. High and low surrogates are correctly dealt with - that is if a high surrogate is randomly chosen, 55296 (d800) to 56191
65   * (db7f) then it is followed by a low surrogate. If a low surrogate is chosen, 56320 (dc00) to 57343 (dfff) then it is placed after a randomly chosen high
66   * surrogate.
67   * </p>
68   * <p>
69   * #ThreadSafe#
70   * </p>
71   *
72   * @see #secure()
73   * @see #secureStrong()
74   * @see #insecure()
75   * @see SecureRandom#SecureRandom()
76   * @see SecureRandom#getInstanceStrong()
77   * @see ThreadLocalRandom#current()
78   * @see RandomUtils
79   * @since 1.0
80   */
81  public class RandomStringUtils {
82  
83      private static final Supplier<RandomUtils> SECURE_SUPPLIER = RandomUtils::secure;
84  
85      private static RandomStringUtils INSECURE = new RandomStringUtils(RandomUtils::insecure);
86  
87      private static RandomStringUtils SECURE = new RandomStringUtils(SECURE_SUPPLIER);
88  
89      private static RandomStringUtils SECURE_STRONG = new RandomStringUtils(RandomUtils::secureStrong);
90  
91      private static final char[] ALPHANUMERICAL_CHARS = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
92              'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
93              'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '0', '1',
94              '2', '3', '4', '5', '6', '7', '8', '9' };
95  
96      /**
97       * Gets the singleton instance based on {@link ThreadLocalRandom#current()}; <b>which is not cryptographically
98       * secure</b>; use {@link #secure()} to use an algorithms/providers specified in the
99       * {@code securerandom.strongAlgorithms} {@link Security} property.
100      * <p>
101      * The method {@link ThreadLocalRandom#current()} is called on-demand.
102      * </p>
103      *
104      * @return the singleton instance based on {@link ThreadLocalRandom#current()}.
105      * @see ThreadLocalRandom#current()
106      * @see #secure()
107      * @since 3.16.0
108      */
109     public static RandomStringUtils insecure() {
110         return INSECURE;
111     }
112 
113     /**
114      * Creates a random string whose length is the number of characters specified.
115      *
116      * <p>
117      * Characters will be chosen from the set of all characters.
118      * </p>
119      *
120      * @param count the length of random string to create
121      * @return the random string
122      * @throws IllegalArgumentException if {@code count} &lt; 0.
123      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
124      */
125     @Deprecated
126     public static String random(final int count) {
127         return secure().next(count);
128     }
129 
130     /**
131      * Creates a random string whose length is the number of characters specified.
132      *
133      * <p>
134      * Characters will be chosen from the set of alpha-numeric characters as indicated by the arguments.
135      * </p>
136      *
137      * @param count   the length of random string to create
138      * @param letters if {@code true}, generated string may include alphabetic characters
139      * @param numbers if {@code true}, generated string may include numeric characters
140      * @return the random string
141      * @throws IllegalArgumentException if {@code count} &lt; 0.
142      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
143      */
144     @Deprecated
145     public static String random(final int count, final boolean letters, final boolean numbers) {
146         return secure().next(count, letters, numbers);
147     }
148 
149     /**
150      * Creates a random string whose length is the number of characters specified.
151      *
152      * <p>
153      * Characters will be chosen from the set of characters specified.
154      * </p>
155      *
156      * @param count the length of random string to create
157      * @param chars the character array containing the set of characters to use, may be null
158      * @return the random string
159      * @throws IllegalArgumentException if {@code count} &lt; 0.
160      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
161      */
162     @Deprecated
163     public static String random(final int count, final char... chars) {
164         return secure().next(count, chars);
165     }
166 
167     /**
168      * Creates a random string whose length is the number of characters specified.
169      *
170      * <p>
171      * Characters will be chosen from the set of alpha-numeric characters as indicated by the arguments.
172      * </p>
173      *
174      * @param count   the length of random string to create
175      * @param start   the position in set of chars to start at
176      * @param end     the position in set of chars to end before
177      * @param letters if {@code true}, generated string may include alphabetic characters
178      * @param numbers if {@code true}, generated string may include numeric characters
179      * @return the random string
180      * @throws IllegalArgumentException if {@code count} &lt; 0.
181      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
182      */
183     @Deprecated
184     public static String random(final int count, final int start, final int end, final boolean letters,
185             final boolean numbers) {
186         return secure().next(count, start, end, letters, numbers);
187     }
188 
189     /**
190      * Creates a random string based on a variety of options, using default source of randomness.
191      *
192      * <p>
193      * This method has exactly the same semantics as {@link #random(int,int,int,boolean,boolean,char[],Random)}, but
194      * instead of using an externally supplied source of randomness, it uses the internal static {@link Random}
195      * instance.
196      * </p>
197      *
198      * @param count   the length of random string to create
199      * @param start   the position in set of chars to start at
200      * @param end     the position in set of chars to end before
201      * @param letters if {@code true}, generated string may include alphabetic characters
202      * @param numbers if {@code true}, generated string may include numeric characters
203      * @param chars   the set of chars to choose randoms from. If {@code null}, then it will use the set of all chars.
204      * @return the random string
205      * @throws ArrayIndexOutOfBoundsException if there are not {@code (end - start) + 1} characters in the set array.
206      * @throws IllegalArgumentException       if {@code count} &lt; 0.
207      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
208      */
209     @Deprecated
210     public static String random(final int count, final int start, final int end, final boolean letters,
211             final boolean numbers, final char... chars) {
212         return secure().next(count, start, end, letters, numbers, chars);
213     }
214 
215     /**
216      * Creates a random string based on a variety of options, using supplied source of randomness.
217      *
218      * <p>
219      * If start and end are both {@code 0}, start and end are set to {@code ' '} and {@code 'z'}, the ASCII printable
220      * characters, will be used, unless letters and numbers are both {@code false}, in which case, start and end are set
221      * to {@code 0} and {@link Character#MAX_CODE_POINT}.
222      *
223      * <p>
224      * If set is not {@code null}, characters between start and end are chosen.
225      * </p>
226      *
227      * <p>
228      * This method accepts a user-supplied {@link Random} instance to use as a source of randomness. By seeding a single
229      * {@link Random} instance with a fixed seed and using it for each call, the same random sequence of strings can be
230      * generated repeatedly and predictably.
231      * </p>
232      *
233      * @param count   the length of random string to create
234      * @param start   the position in set of chars to start at (inclusive)
235      * @param end     the position in set of chars to end before (exclusive)
236      * @param letters if {@code true}, generated string may include alphabetic characters
237      * @param numbers if {@code true}, generated string may include numeric characters
238      * @param chars   the set of chars to choose randoms from, must not be empty. If {@code null}, then it will use the
239      *                set of all chars.
240      * @param random  a source of randomness.
241      * @return the random string
242      * @throws ArrayIndexOutOfBoundsException if there are not {@code (end - start) + 1} characters in the set array.
243      * @throws IllegalArgumentException       if {@code count} &lt; 0 or the provided chars array is empty.
244      * @since 2.0
245      */
246     public static String random(int count, int start, int end, final boolean letters, final boolean numbers,
247             final char[] chars, final Random random) {
248         if (count == 0) {
249             return StringUtils.EMPTY;
250         }
251         if (count < 0) {
252             throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
253         }
254         if (chars != null && chars.length == 0) {
255             throw new IllegalArgumentException("The chars array must not be empty");
256         }
257 
258         if (start == 0 && end == 0) {
259             if (chars != null) {
260                 end = chars.length;
261             } else if (!letters && !numbers) {
262                 end = Character.MAX_CODE_POINT;
263             } else {
264                 end = 'z' + 1;
265                 start = ' ';
266             }
267         } else if (end <= start) {
268             throw new IllegalArgumentException(
269                     "Parameter end (" + end + ") must be greater than start (" + start + ")");
270         } else if (start < 0 || end < 0) {
271             throw new IllegalArgumentException("Character positions MUST be >= 0");
272         }
273 
274         if (end > Character.MAX_CODE_POINT) {
275             // Technically, it should be `Character.MAX_CODE_POINT+1` as `end` is excluded
276             // But the character `Character.MAX_CODE_POINT` is private use, so it would anyway be excluded
277             end = Character.MAX_CODE_POINT;
278         }
279 
280         // Optimize generation of full alphanumerical characters
281         // Normally, we would need to pick a 7-bit integer, since gap = 'z' - '0' + 1 = 75 > 64
282         // In turn, this would make us reject the sampling with probability 1 - 62 / 2^7 > 1 / 2
283         // Instead we can pick directly from the right set of 62 characters, which requires
284         // picking a 6-bit integer and only rejecting with probability 2 / 64 = 1 / 32
285         if (chars == null && letters && numbers && start <= '0' && end >= 'z' + 1) {
286             return random(count, 0, 0, false, false, ALPHANUMERICAL_CHARS, random);
287         }
288 
289         // Optimize start and end when filtering by letters and/or numbers:
290         // The range provided may be too large since we filter anyway afterward.
291         // Note the use of Math.min/max (as opposed to setting start to '0' for example),
292         // since it is possible the range start/end excludes some of the letters/numbers,
293         // e.g., it is possible that start already is '1' when numbers = true, and start
294         // needs to stay equal to '1' in that case.
295         if (chars == null) {
296             if (letters && numbers) {
297                 start = Math.max('0', start);
298                 end = Math.min('z' + 1, end);
299             } else if (numbers) {
300                 // just numbers, no letters
301                 start = Math.max('0', start);
302                 end = Math.min('9' + 1, end);
303             } else if (letters) {
304                 // just letters, no numbers
305                 start = Math.max('A', start);
306                 end = Math.min('z' + 1, end);
307             }
308         }
309 
310         final int zeroDigitAscii = 48;
311         final int firstLetterAscii = 65;
312 
313         if (chars == null && (numbers && end <= zeroDigitAscii || letters && end <= firstLetterAscii)) {
314             throw new IllegalArgumentException(
315                     "Parameter end (" + end + ") must be greater then (" + zeroDigitAscii + ") for generating digits "
316                             + "or greater then (" + firstLetterAscii + ") for generating letters.");
317         }
318 
319         final StringBuilder builder = new StringBuilder(count);
320         final int gap = end - start;
321         final int gapBits = Integer.SIZE - Integer.numberOfLeadingZeros(gap);
322         // The size of the cache we use is an heuristic:
323         // about twice the number of bytes required if no rejection
324         // Ideally the cache size depends on multiple factor, including the cost of generating x bytes
325         // of randomness as well as the probability of rejection. It is however not easy to know
326         // those values programmatically for the general case.
327         final CachedRandomBits arb = new CachedRandomBits((count * gapBits + 3) / 5 + 10, random);
328 
329         while (count-- != 0) {
330             // Generate a random value between start (included) and end (excluded)
331             final int randomValue = arb.nextBits(gapBits) + start;
332             // Rejection sampling if value too large
333             if (randomValue >= end) {
334                 count++;
335                 continue;
336             }
337 
338             final int codePoint;
339             if (chars == null) {
340                 codePoint = randomValue;
341 
342                 switch (Character.getType(codePoint)) {
343                 case Character.UNASSIGNED:
344                 case Character.PRIVATE_USE:
345                 case Character.SURROGATE:
346                     count++;
347                     continue;
348                 }
349 
350             } else {
351                 codePoint = chars[randomValue];
352             }
353 
354             final int numberOfChars = Character.charCount(codePoint);
355             if (count == 0 && numberOfChars > 1) {
356                 count++;
357                 continue;
358             }
359 
360             if (letters && Character.isLetter(codePoint) || numbers && Character.isDigit(codePoint)
361                     || !letters && !numbers) {
362                 builder.appendCodePoint(codePoint);
363 
364                 if (numberOfChars == 2) {
365                     count--;
366                 }
367 
368             } else {
369                 count++;
370             }
371         }
372         return builder.toString();
373     }
374 
375     /**
376      * Creates a random string whose length is the number of characters specified.
377      *
378      * <p>
379      * Characters will be chosen from the set of characters specified by the string, must not be empty. If null, the set
380      * of all characters is used.
381      * </p>
382      *
383      * @param count the length of random string to create
384      * @param chars the String containing the set of characters to use, may be null, but must not be empty
385      * @return the random string
386      * @throws IllegalArgumentException if {@code count} &lt; 0 or the string is empty.
387      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
388      */
389     @Deprecated
390     public static String random(final int count, final String chars) {
391         return secure().next(count, chars);
392     }
393 
394     /**
395      * Creates a random string whose length is the number of characters specified.
396      *
397      * <p>
398      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z).
399      * </p>
400      *
401      * @param count the length of random string to create
402      * @return the random string
403      * @throws IllegalArgumentException if {@code count} &lt; 0.
404      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
405      */
406     @Deprecated
407     public static String randomAlphabetic(final int count) {
408         return secure().nextAlphabetic(count);
409     }
410 
411     /**
412      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
413      *
414      * <p>
415      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z).
416      * </p>
417      *
418      * @param minLengthInclusive the inclusive minimum length of the string to generate
419      * @param maxLengthExclusive the exclusive maximum length of the string to generate
420      * @return the random string
421      * @since 3.5
422      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
423      */
424     @Deprecated
425     public static String randomAlphabetic(final int minLengthInclusive, final int maxLengthExclusive) {
426         return secure().nextAlphabetic(minLengthInclusive, maxLengthExclusive);
427     }
428 
429     /**
430      * Creates a random string whose length is the number of characters specified.
431      *
432      * <p>
433      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z) and the digits 0-9.
434      * </p>
435      *
436      * @param count the length of random string to create
437      * @return the random string
438      * @throws IllegalArgumentException if {@code count} &lt; 0.
439      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
440      */
441     @Deprecated
442     public static String randomAlphanumeric(final int count) {
443         return secure().nextAlphanumeric(count);
444     }
445 
446     /**
447      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
448      *
449      * <p>
450      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z) and the digits 0-9.
451      * </p>
452      *
453      * @param minLengthInclusive the inclusive minimum length of the string to generate
454      * @param maxLengthExclusive the exclusive maximum length of the string to generate
455      * @return the random string
456      * @since 3.5
457      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
458      */
459     @Deprecated
460     public static String randomAlphanumeric(final int minLengthInclusive, final int maxLengthExclusive) {
461         return secure().nextAlphanumeric(minLengthInclusive, maxLengthExclusive);
462     }
463 
464     /**
465      * Creates a random string whose length is the number of characters specified.
466      *
467      * <p>
468      * Characters will be chosen from the set of characters whose ASCII value is between {@code 32} and {@code 126}
469      * (inclusive).
470      * </p>
471      *
472      * @param count the length of random string to create
473      * @return the random string
474      * @throws IllegalArgumentException if {@code count} &lt; 0.
475      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
476      */
477     @Deprecated
478     public static String randomAscii(final int count) {
479         return secure().nextAscii(count);
480     }
481 
482     /**
483      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
484      *
485      * <p>
486      * Characters will be chosen from the set of characters whose ASCII value is between {@code 32} and {@code 126}
487      * (inclusive).
488      * </p>
489      *
490      * @param minLengthInclusive the inclusive minimum length of the string to generate
491      * @param maxLengthExclusive the exclusive maximum length of the string to generate
492      * @return the random string
493      * @since 3.5
494      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
495      */
496     @Deprecated
497     public static String randomAscii(final int minLengthInclusive, final int maxLengthExclusive) {
498         return secure().nextAscii(minLengthInclusive, maxLengthExclusive);
499     }
500 
501     /**
502      * Creates a random string whose length is the number of characters specified.
503      *
504      * <p>
505      * Characters will be chosen from the set of characters which match the POSIX [:graph:] regular expression character
506      * class. This class contains all visible ASCII characters (i.e. anything except spaces and control characters).
507      * </p>
508      *
509      * @param count the length of random string to create
510      * @return the random string
511      * @throws IllegalArgumentException if {@code count} &lt; 0.
512      * @since 3.5
513      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
514      */
515     @Deprecated
516     public static String randomGraph(final int count) {
517         return secure().nextGraph(count);
518     }
519 
520     /**
521      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
522      *
523      * <p>
524      * Characters will be chosen from the set of \p{Graph} characters.
525      * </p>
526      *
527      * @param minLengthInclusive the inclusive minimum length of the string to generate
528      * @param maxLengthExclusive the exclusive maximum length of the string to generate
529      * @return the random string
530      * @since 3.5
531      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
532      */
533     @Deprecated
534     public static String randomGraph(final int minLengthInclusive, final int maxLengthExclusive) {
535         return secure().nextGraph(minLengthInclusive, maxLengthExclusive);
536     }
537 
538     /**
539      * Creates a random string whose length is the number of characters specified.
540      *
541      * <p>
542      * Characters will be chosen from the set of numeric characters.
543      * </p>
544      *
545      * @param count the length of random string to create
546      * @return the random string
547      * @throws IllegalArgumentException if {@code count} &lt; 0.
548      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
549      */
550     @Deprecated
551     public static String randomNumeric(final int count) {
552         return secure().nextNumeric(count);
553     }
554 
555     /**
556      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
557      *
558      * <p>
559      * Characters will be chosen from the set of \p{Digit} characters.
560      * </p>
561      *
562      * @param minLengthInclusive the inclusive minimum length of the string to generate
563      * @param maxLengthExclusive the exclusive maximum length of the string to generate
564      * @return the random string
565      * @since 3.5
566      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
567      */
568     @Deprecated
569     public static String randomNumeric(final int minLengthInclusive, final int maxLengthExclusive) {
570         return secure().nextNumeric(minLengthInclusive, maxLengthExclusive);
571     }
572 
573     /**
574      * Creates a random string whose length is the number of characters specified.
575      *
576      * <p>
577      * Characters will be chosen from the set of characters which match the POSIX [:print:] regular expression character
578      * class. This class includes all visible ASCII characters and spaces (i.e. anything except control characters).
579      * </p>
580      *
581      * @param count the length of random string to create
582      * @return the random string
583      * @throws IllegalArgumentException if {@code count} &lt; 0.
584      * @since 3.5
585      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
586      */
587     @Deprecated
588     public static String randomPrint(final int count) {
589         return secure().nextPrint(count);
590     }
591 
592     /**
593      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
594      *
595      * <p>
596      * Characters will be chosen from the set of \p{Print} characters.
597      * </p>
598      *
599      * @param minLengthInclusive the inclusive minimum length of the string to generate
600      * @param maxLengthExclusive the exclusive maximum length of the string to generate
601      * @return the random string
602      * @since 3.5
603      * @deprecated Use {@link #secure()}, {@link #secureStrong()},or {@link #insecure()}.
604      */
605     @Deprecated
606     public static String randomPrint(final int minLengthInclusive, final int maxLengthExclusive) {
607         return secure().nextPrint(minLengthInclusive, maxLengthExclusive);
608     }
609 
610     /**
611      * Gets the singleton instance based on {@link SecureRandom#SecureRandom()} which uses a secure random number generator (RNG) implementing the default
612      * random number algorithm.
613      * <p>
614      * The method {@link SecureRandom#SecureRandom()} is called on-demand.
615      * </p>
616      *
617      * @return the singleton instance based on {@link SecureRandom#SecureRandom()}.
618      * @see SecureRandom#SecureRandom()
619      * @since 3.16.0
620      */
621     public static RandomStringUtils secure() {
622         return SECURE;
623     }
624 
625     /**
626      * Gets the singleton instance based on {@link SecureRandom#getInstanceStrong()} which uses an algorithms/providers
627      * specified in the {@code securerandom.strongAlgorithms} {@link Security} property.
628      * <p>
629      * The method {@link SecureRandom#getInstanceStrong()} is called on-demand.
630      * </p>
631      *
632      * @return the singleton instance based on {@link SecureRandom#getInstanceStrong()}.
633      * @see SecureRandom#getInstanceStrong()
634      * @since 3.17.0
635      */
636     public static RandomStringUtils secureStrong() {
637         return SECURE_STRONG;
638     }
639 
640     private final Supplier<RandomUtils> random;
641 
642     /**
643      * {@link RandomStringUtils} instances should NOT be constructed in standard programming. Instead, the class should
644      * be used as {@code RandomStringUtils.random(5);}.
645      *
646      * <p>
647      * This constructor is public to permit tools that require a JavaBean instance to operate.
648      * </p>
649      *
650      * @deprecated TODO Make private in 4.0.
651      */
652     @Deprecated
653     public RandomStringUtils() {
654         this(SECURE_SUPPLIER);
655     }
656 
657     private RandomStringUtils(final Supplier<RandomUtils> random) {
658         this.random = random;
659     }
660 
661     /**
662      * Creates a random string whose length is the number of characters specified.
663      *
664      * <p>
665      * Characters will be chosen from the set of all characters.
666      * </p>
667      *
668      * @param count the length of random string to create
669      * @return the random string
670      * @throws IllegalArgumentException if {@code count} &lt; 0.
671      * @since 3.16.0
672      */
673     public String next(final int count) {
674         return next(count, false, false);
675     }
676 
677     /**
678      * Creates a random string whose length is the number of characters specified.
679      *
680      * <p>
681      * Characters will be chosen from the set of alpha-numeric characters as indicated by the arguments.
682      * </p>
683      *
684      * @param count   the length of random string to create
685      * @param letters if {@code true}, generated string may include alphabetic characters
686      * @param numbers if {@code true}, generated string may include numeric characters
687      * @return the random string
688      * @throws IllegalArgumentException if {@code count} &lt; 0.
689      * @since 3.16.0
690      */
691     public String next(final int count, final boolean letters, final boolean numbers) {
692         return next(count, 0, 0, letters, numbers);
693     }
694 
695     /**
696      * Creates a random string whose length is the number of characters specified.
697      *
698      * <p>
699      * Characters will be chosen from the set of characters specified.
700      * </p>
701      *
702      * @param count the length of random string to create
703      * @param chars the character array containing the set of characters to use, may be null
704      * @return the random string
705      * @throws IllegalArgumentException if {@code count} &lt; 0.
706      * @since 3.16.0
707      */
708     public String next(final int count, final char... chars) {
709         if (chars == null) {
710             return random(count, 0, 0, false, false, null, random());
711         }
712         return random(count, 0, chars.length, false, false, chars, random());
713     }
714 
715     /**
716      * Creates a random string whose length is the number of characters specified.
717      *
718      * <p>
719      * Characters will be chosen from the set of alpha-numeric characters as indicated by the arguments.
720      * </p>
721      *
722      * @param count   the length of random string to create
723      * @param start   the position in set of chars to start at
724      * @param end     the position in set of chars to end before
725      * @param letters if {@code true}, generated string may include alphabetic characters
726      * @param numbers if {@code true}, generated string may include numeric characters
727      * @return the random string
728      * @throws IllegalArgumentException if {@code count} &lt; 0.
729      * @since 3.16.0
730      */
731     public String next(final int count, final int start, final int end, final boolean letters, final boolean numbers) {
732         return random(count, start, end, letters, numbers, null, random());
733     }
734 
735     /**
736      * Creates a random string based on a variety of options, using default source of randomness.
737      *
738      * <p>
739      * This method has exactly the same semantics as {@link #random(int,int,int,boolean,boolean,char[],Random)}, but
740      * instead of using an externally supplied source of randomness, it uses the internal static {@link Random}
741      * instance.
742      * </p>
743      *
744      * @param count   the length of random string to create
745      * @param start   the position in set of chars to start at
746      * @param end     the position in set of chars to end before
747      * @param letters if {@code true}, generated string may include alphabetic characters
748      * @param numbers if {@code true}, generated string may include numeric characters
749      * @param chars   the set of chars to choose randoms from. If {@code null}, then it will use the set of all chars.
750      * @return the random string
751      * @throws ArrayIndexOutOfBoundsException if there are not {@code (end - start) + 1} characters in the set array.
752      * @throws IllegalArgumentException       if {@code count} &lt; 0.
753      */
754     public String next(final int count, final int start, final int end, final boolean letters, final boolean numbers,
755             final char... chars) {
756         return random(count, start, end, letters, numbers, chars, random());
757     }
758 
759     /**
760      * Creates a random string whose length is the number of characters specified.
761      *
762      * <p>
763      * Characters will be chosen from the set of characters specified by the string, must not be empty. If null, the set
764      * of all characters is used.
765      * </p>
766      *
767      * @param count the length of random string to create
768      * @param chars the String containing the set of characters to use, may be null, but must not be empty
769      * @return the random string
770      * @throws IllegalArgumentException if {@code count} &lt; 0 or the string is empty.
771      * @since 3.16.0
772      */
773     public String next(final int count, final String chars) {
774         if (chars == null) {
775             return random(count, 0, 0, false, false, null, random());
776         }
777         return next(count, chars.toCharArray());
778     }
779 
780     /**
781      * Creates a random string whose length is the number of characters specified.
782      *
783      * <p>
784      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z).
785      * </p>
786      *
787      * @param count the length of random string to create
788      * @return the random string
789      * @throws IllegalArgumentException if {@code count} &lt; 0.
790      */
791     public String nextAlphabetic(final int count) {
792         return next(count, true, false);
793     }
794 
795     /**
796      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
797      *
798      * <p>
799      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z).
800      * </p>
801      *
802      * @param minLengthInclusive the inclusive minimum length of the string to generate
803      * @param maxLengthExclusive the exclusive maximum length of the string to generate
804      * @return the random string
805      * @since 3.5
806      */
807     public String nextAlphabetic(final int minLengthInclusive, final int maxLengthExclusive) {
808         return nextAlphabetic(randomUtils().randomInt(minLengthInclusive, maxLengthExclusive));
809     }
810 
811     /**
812      * Creates a random string whose length is the number of characters specified.
813      *
814      * <p>
815      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z) and the digits 0-9.
816      * </p>
817      *
818      * @param count the length of random string to create
819      * @return the random string
820      * @throws IllegalArgumentException if {@code count} &lt; 0.
821      */
822     public String nextAlphanumeric(final int count) {
823         return next(count, true, true);
824     }
825 
826     /**
827      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
828      *
829      * <p>
830      * Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z) and the digits 0-9.
831      * </p>
832      *
833      * @param minLengthInclusive the inclusive minimum length of the string to generate
834      * @param maxLengthExclusive the exclusive maximum length of the string to generate
835      * @return the random string
836      * @since 3.5
837      */
838     public String nextAlphanumeric(final int minLengthInclusive, final int maxLengthExclusive) {
839         return nextAlphanumeric(randomUtils().randomInt(minLengthInclusive, maxLengthExclusive));
840     }
841 
842     /**
843      * Creates a random string whose length is the number of characters specified.
844      *
845      * <p>
846      * Characters will be chosen from the set of characters whose ASCII value is between {@code 32} and {@code 126}
847      * (inclusive).
848      * </p>
849      *
850      * @param count the length of random string to create
851      * @return the random string
852      * @throws IllegalArgumentException if {@code count} &lt; 0.
853      */
854     public String nextAscii(final int count) {
855         return next(count, 32, 127, false, false);
856     }
857 
858     /**
859      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
860      *
861      * <p>
862      * Characters will be chosen from the set of characters whose ASCII value is between {@code 32} and {@code 126}
863      * (inclusive).
864      * </p>
865      *
866      * @param minLengthInclusive the inclusive minimum length of the string to generate
867      * @param maxLengthExclusive the exclusive maximum length of the string to generate
868      * @return the random string
869      * @since 3.5
870      */
871     public String nextAscii(final int minLengthInclusive, final int maxLengthExclusive) {
872         return nextAscii(randomUtils().randomInt(minLengthInclusive, maxLengthExclusive));
873     }
874 
875     /**
876      * Creates a random string whose length is the number of characters specified.
877      *
878      * <p>
879      * Characters will be chosen from the set of characters which match the POSIX [:graph:] regular expression character
880      * class. This class contains all visible ASCII characters (i.e. anything except spaces and control characters).
881      * </p>
882      *
883      * @param count the length of random string to create
884      * @return the random string
885      * @throws IllegalArgumentException if {@code count} &lt; 0.
886      * @since 3.5
887      */
888     public String nextGraph(final int count) {
889         return next(count, 33, 126, false, false);
890     }
891 
892     /**
893      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
894      *
895      * <p>
896      * Characters will be chosen from the set of \p{Graph} characters.
897      * </p>
898      *
899      * @param minLengthInclusive the inclusive minimum length of the string to generate
900      * @param maxLengthExclusive the exclusive maximum length of the string to generate
901      * @return the random string
902      * @since 3.5
903      */
904     public String nextGraph(final int minLengthInclusive, final int maxLengthExclusive) {
905         return nextGraph(randomUtils().randomInt(minLengthInclusive, maxLengthExclusive));
906     }
907 
908     /**
909      * Creates a random string whose length is the number of characters specified.
910      *
911      * <p>
912      * Characters will be chosen from the set of numeric characters.
913      * </p>
914      *
915      * @param count the length of random string to create
916      * @return the random string
917      * @throws IllegalArgumentException if {@code count} &lt; 0.
918      */
919     public String nextNumeric(final int count) {
920         return next(count, false, true);
921     }
922 
923     /**
924      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
925      *
926      * <p>
927      * Characters will be chosen from the set of \p{Digit} characters.
928      * </p>
929      *
930      * @param minLengthInclusive the inclusive minimum length of the string to generate
931      * @param maxLengthExclusive the exclusive maximum length of the string to generate
932      * @return the random string
933      * @since 3.5
934      */
935     public String nextNumeric(final int minLengthInclusive, final int maxLengthExclusive) {
936         return nextNumeric(randomUtils().randomInt(minLengthInclusive, maxLengthExclusive));
937     }
938 
939     /**
940      * Creates a random string whose length is the number of characters specified.
941      *
942      * <p>
943      * Characters will be chosen from the set of characters which match the POSIX [:print:] regular expression character
944      * class. This class includes all visible ASCII characters and spaces (i.e. anything except control characters).
945      * </p>
946      *
947      * @param count the length of random string to create
948      * @return the random string
949      * @throws IllegalArgumentException if {@code count} &lt; 0.
950      * @since 3.5
951      * @since 3.16.0
952      */
953     public String nextPrint(final int count) {
954         return next(count, 32, 126, false, false);
955     }
956 
957     /**
958      * Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
959      *
960      * <p>
961      * Characters will be chosen from the set of \p{Print} characters.
962      * </p>
963      *
964      * @param minLengthInclusive the inclusive minimum length of the string to generate
965      * @param maxLengthExclusive the exclusive maximum length of the string to generate
966      * @return the random string
967      * @since 3.16.0
968      */
969     public String nextPrint(final int minLengthInclusive, final int maxLengthExclusive) {
970         return nextPrint(randomUtils().randomInt(minLengthInclusive, maxLengthExclusive));
971     }
972 
973     /**
974      * Gets the Random.
975      *
976      * @return the Random.
977      */
978     private Random random() {
979         return randomUtils().random();
980     }
981 
982     /**
983      * Gets the RandomUtils.
984      *
985      * @return the RandomUtils.
986      */
987     private RandomUtils randomUtils() {
988         return random.get();
989     }
990 
991     @Override
992     public String toString() {
993         return "RandomStringUtils [random=" + random() + "]";
994     }
995 
996 }