001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.lang3;
018
019import java.util.Random;
020
021/**
022 * <p>Generates random {@code String}s.</p>
023 *
024 * <p><b>Caveat: Instances of {@link Random}, upon which the implementation of this
025 * class relies, are not cryptographically secure.</b></p>
026 *
027 * <p>RandomStringUtils is intended for simple use cases. For more advanced
028 * use cases consider using Apache Commons Text's
029 * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/RandomStringGenerator.html">
030 * RandomStringGenerator</a> instead.</p>
031 *
032 * <p>The Apache Commons project provides
033 * <a href="https://commons.apache.org/rng">Commons RNG</a> dedicated to pseudo-random number generation, that may be
034 * a better choice for applications with more stringent requirements
035 * (performance and/or correctness).</p>
036 *
037 * <p>Note that <em>private high surrogate</em> characters are ignored.
038 * These are Unicode characters that fall between the values 56192 (db80)
039 * and 56319 (dbff) as we don't know how to handle them.
040 * High and low surrogates are correctly dealt with - that is if a
041 * high surrogate is randomly chosen, 55296 (d800) to 56191 (db7f)
042 * then it is followed by a low surrogate. If a low surrogate is chosen,
043 * 56320 (dc00) to 57343 (dfff) then it is placed after a randomly
044 * chosen high surrogate.</p>
045 *
046 * <p>#ThreadSafe#</p>
047 * @since 1.0
048 */
049public class RandomStringUtils {
050
051    /**
052     * <p>Random object used by random method. This has to be not local
053     * to the random method so as to not return the same value in the
054     * same millisecond.</p>
055     */
056    private static final Random RANDOM = new Random();
057
058    /**
059     * <p>{@code RandomStringUtils} instances should NOT be constructed in
060     * standard programming. Instead, the class should be used as
061     * {@code RandomStringUtils.random(5);}.</p>
062     *
063     * <p>This constructor is public to permit tools that require a JavaBean instance
064     * to operate.</p>
065     */
066    public RandomStringUtils() {
067      super();
068    }
069
070    // Random
071    //-----------------------------------------------------------------------
072    /**
073     * <p>Creates a random string whose length is the number of characters
074     * specified.</p>
075     *
076     * <p>Characters will be chosen from the set of all characters.</p>
077     *
078     * @param count  the length of random string to create
079     * @return the random string
080     */
081    public static String random(final int count) {
082        return random(count, false, false);
083    }
084
085    /**
086     * <p>Creates a random string whose length is the number of characters
087     * specified.</p>
088     *
089     * <p>Characters will be chosen from the set of characters whose
090     * ASCII value is between {@code 32} and {@code 126} (inclusive).</p>
091     *
092     * @param count  the length of random string to create
093     * @return the random string
094     */
095    public static String randomAscii(final int count) {
096        return random(count, 32, 127, false, false);
097    }
098
099    /**
100     * <p>Creates a random string whose length is between the inclusive minimum and
101     * the exclusive maximum.</p>
102     *
103     * <p>Characters will be chosen from the set of characters whose
104     * ASCII value is between {@code 32} and {@code 126} (inclusive).</p>
105     *
106     * @param minLengthInclusive the inclusive minimum length of the string to generate
107     * @param maxLengthExclusive the exclusive maximum length of the string to generate
108     * @return the random string
109     * @since 3.5
110     */
111    public static String randomAscii(final int minLengthInclusive, final int maxLengthExclusive) {
112        return randomAscii(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive));
113    }
114
115    /**
116     * <p>Creates a random string whose length is the number of characters
117     * specified.</p>
118     *
119     * <p>Characters will be chosen from the set of Latin alphabetic
120     * characters (a-z, A-Z).</p>
121     *
122     * @param count  the length of random string to create
123     * @return the random string
124     */
125    public static String randomAlphabetic(final int count) {
126        return random(count, true, false);
127    }
128
129    /**
130     * <p>Creates a random string whose length is between the inclusive minimum and
131     * the exclusive maximum.</p>
132     *
133     * <p>Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z).</p>
134     *
135     * @param minLengthInclusive the inclusive minimum length of the string to generate
136     * @param maxLengthExclusive the exclusive maximum length of the string to generate
137     * @return the random string
138     * @since 3.5
139     */
140    public static String randomAlphabetic(final int minLengthInclusive, final int maxLengthExclusive) {
141        return randomAlphabetic(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive));
142    }
143
144    /**
145     * <p>Creates a random string whose length is the number of characters
146     * specified.</p>
147     *
148     * <p>Characters will be chosen from the set of Latin alphabetic
149     * characters (a-z, A-Z) and the digits 0-9.</p>
150     *
151     * @param count  the length of random string to create
152     * @return the random string
153     */
154    public static String randomAlphanumeric(final int count) {
155        return random(count, true, true);
156    }
157
158    /**
159     * <p>Creates a random string whose length is between the inclusive minimum and
160     * the exclusive maximum.</p>
161     *
162     * <p>Characters will be chosen from the set of Latin alphabetic
163     * characters (a-z, A-Z) and the digits 0-9.</p>
164     *
165     * @param minLengthInclusive the inclusive minimum length of the string to generate
166     * @param maxLengthExclusive the exclusive maximum length of the string to generate
167     * @return the random string
168     * @since 3.5
169     */
170    public static String randomAlphanumeric(final int minLengthInclusive, final int maxLengthExclusive) {
171        return randomAlphanumeric(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive));
172    }
173
174    /**
175     * <p>Creates a random string whose length is the number of characters specified.</p>
176     *
177     * <p>Characters will be chosen from the set of characters which match the POSIX [:graph:]
178     * regular expression character class. This class contains all visible ASCII characters
179     * (i.e. anything except spaces and control characters).</p>
180     *
181     * @param count  the length of random string to create
182     * @return the random string
183     * @since 3.5
184     */
185    public static String randomGraph(final int count) {
186        return random(count, 33, 126, false, false);
187    }
188
189    /**
190     * <p>Creates a random string whose length is between the inclusive minimum and
191     * the exclusive maximum.</p>
192     *
193     * <p>Characters will be chosen from the set of \p{Graph} characters.</p>
194     *
195     * @param minLengthInclusive the inclusive minimum length of the string to generate
196     * @param maxLengthExclusive the exclusive maximum length of the string to generate
197     * @return the random string
198     * @since 3.5
199     */
200    public static String randomGraph(final int minLengthInclusive, final int maxLengthExclusive) {
201        return randomGraph(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive));
202    }
203
204    /**
205     * <p>Creates a random string whose length is the number of characters
206     * specified.</p>
207     *
208     * <p>Characters will be chosen from the set of numeric
209     * characters.</p>
210     *
211     * @param count  the length of random string to create
212     * @return the random string
213     */
214    public static String randomNumeric(final int count) {
215        return random(count, false, true);
216    }
217
218    /**
219     * <p>Creates a random string whose length is between the inclusive minimum and
220     * the exclusive maximum.</p>
221     *
222     * <p>Characters will be chosen from the set of \p{Digit} characters.</p>
223     *
224     * @param minLengthInclusive the inclusive minimum length of the string to generate
225     * @param maxLengthExclusive the exclusive maximum length of the string to generate
226     * @return the random string
227     * @since 3.5
228     */
229    public static String randomNumeric(final int minLengthInclusive, final int maxLengthExclusive) {
230        return randomNumeric(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive));
231    }
232
233    /**
234     * <p>Creates a random string whose length is the number of characters specified.</p>
235     *
236     * <p>Characters will be chosen from the set of characters which match the POSIX [:print:]
237     * regular expression character class. This class includes all visible ASCII characters and spaces
238     * (i.e. anything except control characters).</p>
239     *
240     * @param count  the length of random string to create
241     * @return the random string
242     * @since 3.5
243     */
244    public static String randomPrint(final int count) {
245        return random(count, 32, 126, false, false);
246    }
247
248    /**
249     * <p>Creates a random string whose length is between the inclusive minimum and
250     * the exclusive maximum.</p>
251     *
252     * <p>Characters will be chosen from the set of \p{Print} characters.</p>
253     *
254     * @param minLengthInclusive the inclusive minimum length of the string to generate
255     * @param maxLengthExclusive the exclusive maximum length of the string to generate
256     * @return the random string
257     * @since 3.5
258     */
259    public static String randomPrint(final int minLengthInclusive, final int maxLengthExclusive) {
260        return randomPrint(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive));
261    }
262
263    /**
264     * <p>Creates a random string whose length is the number of characters
265     * specified.</p>
266     *
267     * <p>Characters will be chosen from the set of alpha-numeric
268     * characters as indicated by the arguments.</p>
269     *
270     * @param count  the length of random string to create
271     * @param letters  if {@code true}, generated string may include
272     *  alphabetic characters
273     * @param numbers  if {@code true}, generated string may include
274     *  numeric characters
275     * @return the random string
276     */
277    public static String random(final int count, final boolean letters, final boolean numbers) {
278        return random(count, 0, 0, letters, numbers);
279    }
280
281    /**
282     * <p>Creates a random string whose length is the number of characters
283     * specified.</p>
284     *
285     * <p>Characters will be chosen from the set of alpha-numeric
286     * characters as indicated by the arguments.</p>
287     *
288     * @param count  the length of random string to create
289     * @param start  the position in set of chars to start at
290     * @param end  the position in set of chars to end before
291     * @param letters  if {@code true}, generated string may include
292     *  alphabetic characters
293     * @param numbers  if {@code true}, generated string may include
294     *  numeric characters
295     * @return the random string
296     */
297    public static String random(final int count, final int start, final int end, final boolean letters, final boolean numbers) {
298        return random(count, start, end, letters, numbers, null, RANDOM);
299    }
300
301    /**
302     * <p>Creates a random string based on a variety of options, using
303     * default source of randomness.</p>
304     *
305     * <p>This method has exactly the same semantics as
306     * {@link #random(int,int,int,boolean,boolean,char[],Random)}, but
307     * instead of using an externally supplied source of randomness, it uses
308     * the internal static {@link Random} instance.</p>
309     *
310     * @param count  the length of random string to create
311     * @param start  the position in set of chars to start at
312     * @param end  the position in set of chars to end before
313     * @param letters  only allow letters?
314     * @param numbers  only allow numbers?
315     * @param chars  the set of chars to choose randoms from.
316     *  If {@code null}, then it will use the set of all chars.
317     * @return the random string
318     * @throws ArrayIndexOutOfBoundsException if there are not
319     *  {@code (end - start) + 1} characters in the set array.
320     */
321    public static String random(final int count, final int start, final int end, final boolean letters, final boolean numbers, final char... chars) {
322        return random(count, start, end, letters, numbers, chars, RANDOM);
323    }
324
325    /**
326     * <p>Creates a random string based on a variety of options, using
327     * supplied source of randomness.</p>
328     *
329     * <p>If start and end are both {@code 0}, start and end are set
330     * to {@code ' '} and {@code 'z'}, the ASCII printable
331     * characters, will be used, unless letters and numbers are both
332     * {@code false}, in which case, start and end are set to
333     * {@code 0} and {@link Character#MAX_CODE_POINT}.
334     *
335     * <p>If set is not {@code null}, characters between start and
336     * end are chosen.</p>
337     *
338     * <p>This method accepts a user-supplied {@link Random}
339     * instance to use as a source of randomness. By seeding a single
340     * {@link Random} instance with a fixed seed and using it for each call,
341     * the same random sequence of strings can be generated repeatedly
342     * and predictably.</p>
343     *
344     * @param count  the length of random string to create
345     * @param start  the position in set of chars to start at (inclusive)
346     * @param end  the position in set of chars to end before (exclusive)
347     * @param letters  only allow letters?
348     * @param numbers  only allow numbers?
349     * @param chars  the set of chars to choose randoms from, must not be empty.
350     *  If {@code null}, then it will use the set of all chars.
351     * @param random  a source of randomness.
352     * @return the random string
353     * @throws ArrayIndexOutOfBoundsException if there are not
354     *  {@code (end - start) + 1} characters in the set array.
355     * @throws IllegalArgumentException if {@code count} &lt; 0 or the provided chars array is empty.
356     * @since 2.0
357     */
358    public static String random(int count, int start, int end, final boolean letters, final boolean numbers,
359                                final char[] chars, final Random random) {
360        if (count == 0) {
361            return StringUtils.EMPTY;
362        } else if (count < 0) {
363            throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
364        }
365        if (chars != null && chars.length == 0) {
366            throw new IllegalArgumentException("The chars array must not be empty");
367        }
368
369        if (start == 0 && end == 0) {
370            if (chars != null) {
371                end = chars.length;
372            } else {
373                if (!letters && !numbers) {
374                    end = Character.MAX_CODE_POINT;
375                } else {
376                    end = 'z' + 1;
377                    start = ' ';
378                }
379            }
380        } else {
381            if (end <= start) {
382                throw new IllegalArgumentException("Parameter end (" + end + ") must be greater than start (" + start + ")");
383            }
384        }
385
386        final int zero_digit_ascii = 48;
387        final int first_letter_ascii = 65;
388
389        if (chars == null && (numbers && end <= zero_digit_ascii
390                || letters && end <= first_letter_ascii)) {
391            throw new IllegalArgumentException("Parameter end (" + end + ") must be greater then (" + zero_digit_ascii + ") for generating digits " +
392                    "or greater then (" + first_letter_ascii + ") for generating letters.");
393        }
394
395        final StringBuilder builder = new StringBuilder(count);
396        final int gap = end - start;
397
398        while (count-- != 0) {
399            int codePoint;
400            if (chars == null) {
401                codePoint = random.nextInt(gap) + start;
402
403                switch (Character.getType(codePoint)) {
404                case Character.UNASSIGNED:
405                case Character.PRIVATE_USE:
406                case Character.SURROGATE:
407                    count++;
408                    continue;
409                }
410
411            } else {
412                codePoint = chars[random.nextInt(gap) + start];
413            }
414
415            final int numberOfChars = Character.charCount(codePoint);
416            if (count == 0 && numberOfChars > 1) {
417                count++;
418                continue;
419            }
420
421            if (letters && Character.isLetter(codePoint)
422                    || numbers && Character.isDigit(codePoint)
423                    || !letters && !numbers) {
424                builder.appendCodePoint(codePoint);
425
426                if (numberOfChars == 2) {
427                    count--;
428                }
429
430            } else {
431                count++;
432            }
433        }
434        return builder.toString();
435    }
436
437
438    /**
439     * <p>Creates a random string whose length is the number of characters
440     * specified.</p>
441     *
442     * <p>Characters will be chosen from the set of characters
443     * specified by the string, must not be empty.
444     * If null, the set of all characters is used.</p>
445     *
446     * @param count  the length of random string to create
447     * @param chars  the String containing the set of characters to use,
448     *  may be null, but must not be empty
449     * @return the random string
450     * @throws IllegalArgumentException if {@code count} &lt; 0 or the string is empty.
451     */
452    public static String random(final int count, final String chars) {
453        if (chars == null) {
454            return random(count, 0, 0, false, false, null, RANDOM);
455        }
456        return random(count, chars.toCharArray());
457    }
458
459    /**
460     * <p>Creates a random string whose length is the number of characters
461     * specified.</p>
462     *
463     * <p>Characters will be chosen from the set of characters specified.</p>
464     *
465     * @param count  the length of random string to create
466     * @param chars  the character array containing the set of characters to use,
467     *  may be null
468     * @return the random string
469     * @throws IllegalArgumentException if {@code count} &lt; 0.
470     */
471    public static String random(final int count, final char... chars) {
472        if (chars == null) {
473            return random(count, 0, 0, false, false, null, RANDOM);
474        }
475        return random(count, 0, chars.length, false, false, chars, RANDOM);
476    }
477
478}