    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     */
    017    package org.apache.commons.lang3;
    018
    019    import java.util.Random;
    020
    021    /**
    022     * <p>Operations for random {@code String}s.</p>
    023     * <p>Currently <em>private high surrogate</em> characters are ignored.
    024     * These are Unicode characters that fall between the values 56192 (db80)
    025     * and 56319 (dbff) as we don't know how to handle them.
    026     * High and low surrogates are correctly dealt with - that is if a
    027     * high surrogate is randomly chosen, 55296 (d800) to 56191 (db7f)
    028     * then it is followed by a low surrogate. If a low surrogate is chosen,
    029     * 56320 (dc00) to 57343 (dfff) then it is placed after a randomly
    030     * chosen high surrogate. </p>
    031     *
    032     * <p>#ThreadSafe#</p>
    033     * @since 1.0
    034     * @version $Id: RandomStringUtils.java 1199894 2011-11-09 17:53:59Z ggregory $
    035     */
    036    public class RandomStringUtils {
    037
    038        /**
    039         * <p>Random object used by random method. This has to be not local
    040         * to the random method so as to not return the same value in the
    041         * same millisecond.</p>
    042         */
    043        private static final Random RANDOM = new Random();
    044
    045        /**
    046         * <p>{@code RandomStringUtils} instances should NOT be constructed in
    047         * standard programming. Instead, the class should be used as
    048         * {@code RandomStringUtils.random(5);}.</p>
    049         *
    050         * <p>This constructor is public to permit tools that require a JavaBean instance
    051         * to operate.</p>
    052         */
    053        public RandomStringUtils() {
    054          super();
    055        }
    056
    057        // Random
    058        //-----------------------------------------------------------------------
    059        /**
    060         * <p>Creates a random string whose length is the number of characters
    061         * specified.</p>
    062         *
    063         * <p>Characters will be chosen from the set of all characters.</p>
    064         *
    065         * @param count  the length of random string to create
    066         * @return the random string
    067         */
    068        public static String random(int count) {
    069            return random(count, false, false);
    070        }
    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 characters whose
    077         * ASCII value is between {@code 32} and {@code 126} (inclusive).</p>
    078         *
    079         * @param count  the length of random string to create
    080         * @return the random string
    081         */
    082        public static String randomAscii(int count) {
    083            return random(count, 32, 127, false, false);
    084        }
    085
    086        /**
    087         * <p>Creates a random string whose length is the number of characters
    088         * specified.</p>
    089         *
    090         * <p>Characters will be chosen from the set of alphabetic
    091         * characters.</p>
    092         *
    093         * @param count  the length of random string to create
    094         * @return the random string
    095         */
    096        public static String randomAlphabetic(int count) {
    097            return random(count, true, false);
    098        }
    099
    100        /**
    101         * <p>Creates a random string whose length is the number of characters
    102         * specified.</p>
    103         *
    104         * <p>Characters will be chosen from the set of alpha-numeric
    105         * characters.</p>
    106         *
    107         * @param count  the length of random string to create
    108         * @return the random string
    109         */
    110        public static String randomAlphanumeric(int count) {
    111            return random(count, true, true);
    112        }
    113
    114        /**
    115         * <p>Creates a random string whose length is the number of characters
    116         * specified.</p>
    117         *
    118         * <p>Characters will be chosen from the set of numeric
    119         * characters.</p>
    120         *
    121         * @param count  the length of random string to create
    122         * @return the random string
    123         */
    124        public static String randomNumeric(int count) {
    125            return random(count, false, true);
    126        }
    127
    128        /**
    129         * <p>Creates a random string whose length is the number of characters
    130         * specified.</p>
    131         *
    132         * <p>Characters will be chosen from the set of alpha-numeric
    133         * characters as indicated by the arguments.</p>
    134         *
    135         * @param count  the length of random string to create
    136         * @param letters  if {@code true}, generated string will include
    137         *  alphabetic characters
    138         * @param numbers  if {@code true}, generated string will include
    139         *  numeric characters
    140         * @return the random string
    141         */
    142        public static String random(int count, boolean letters, boolean numbers) {
    143            return random(count, 0, 0, letters, numbers);
    144        }
    145
    146        /**
    147         * <p>Creates a random string whose length is the number of characters
    148         * specified.</p>
    149         *
    150         * <p>Characters will be chosen from the set of alpha-numeric
    151         * characters as indicated by the arguments.</p>
    152         *
    153         * @param count  the length of random string to create
    154         * @param start  the position in set of chars to start at
    155         * @param end  the position in set of chars to end before
    156         * @param letters  if {@code true}, generated string will include
    157         *  alphabetic characters
    158         * @param numbers  if {@code true}, generated string will include
    159         *  numeric characters
    160         * @return the random string
    161         */
    162        public static String random(int count, int start, int end, boolean letters, boolean numbers) {
    163            return random(count, start, end, letters, numbers, null, RANDOM);
    164        }
    165
    166        /**
    167         * <p>Creates a random string based on a variety of options, using
    168         * default source of randomness.</p>
    169         *
    170         * <p>This method has exactly the same semantics as
    171         * {@link #random(int,int,int,boolean,boolean,char[],Random)}, but
    172         * instead of using an externally supplied source of randomness, it uses
    173         * the internal static {@link Random} instance.</p>
    174         *
    175         * @param count  the length of random string to create
    176         * @param start  the position in set of chars to start at
    177         * @param end  the position in set of chars to end before
    178         * @param letters  only allow letters?
    179         * @param numbers  only allow numbers?
    180         * @param chars  the set of chars to choose randoms from.
    181         *  If {@code null}, then it will use the set of all chars.
    182         * @return the random string
    183         * @throws ArrayIndexOutOfBoundsException if there are not
    184         *  {@code (end - start) + 1} characters in the set array.
    185         */
    186        public static String random(int count, int start, int end, boolean letters, boolean numbers, char... chars) {
    187            return random(count, start, end, letters, numbers, chars, RANDOM);
    188        }
    189
    190        /**
    191         * <p>Creates a random string based on a variety of options, using
    192         * supplied source of randomness.</p>
    193         *
    194         * <p>If start and end are both {@code 0}, start and end are set
    195         * to {@code ' '} and {@code 'z'}, the ASCII printable
    196         * characters, will be used, unless letters and numbers are both
    197         * {@code false}, in which case, start and end are set to
    198         * {@code 0} and {@code Integer.MAX_VALUE}.
    199         *
    200         * <p>If set is not {@code null}, characters between start and
    201         * end are chosen.</p>
    202         *
    203         * <p>This method accepts a user-supplied {@link Random}
    204         * instance to use as a source of randomness. By seeding a single
    205         * {@link Random} instance with a fixed seed and using it for each call,
    206         * the same random sequence of strings can be generated repeatedly
    207         * and predictably.</p>
    208         *
    209         * @param count  the length of random string to create
    210         * @param start  the position in set of chars to start at
    211         * @param end  the position in set of chars to end before
    212         * @param letters  only allow letters?
    213         * @param numbers  only allow numbers?
    214         * @param chars  the set of chars to choose randoms from.
    215         *  If {@code null}, then it will use the set of all chars.
    216         * @param random  a source of randomness.
    217         * @return the random string
    218         * @throws ArrayIndexOutOfBoundsException if there are not
    219         *  {@code (end - start) + 1} characters in the set array.
    220         * @throws IllegalArgumentException if {@code count} &lt; 0.
    221         * @since 2.0
    222         */
    223        public static String random(int count, int start, int end, boolean letters, boolean numbers,
    224                                    char[] chars, Random random) {
    225            if (count == 0) {
    226                return "";
    227            } else if (count < 0) {
    228                throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
    229            }
    230            if (start == 0 && end == 0) {
    231                end = 'z' + 1;
    232                start = ' ';
    233                if (!letters && !numbers) {
    234                    start = 0;
    235                    end = Integer.MAX_VALUE;
    236                }
    237            }
    238
    239            char[] buffer = new char[count];
    240            int gap = end - start;
    241
    242            while (count-- != 0) {
    243                char ch;
    244                if (chars == null) {
    245                    ch = (char) (random.nextInt(gap) + start);
    246                } else {
    247                    ch = chars[random.nextInt(gap) + start];
    248                }
    249                if (letters && Character.isLetter(ch)
    250                        || numbers && Character.isDigit(ch)
    251                        || !letters && !numbers) {
    252                    if(ch >= 56320 && ch <= 57343) {
    253                        if(count == 0) {
    254                            count++;
    255                        } else {
    256                            // low surrogate, insert high surrogate after putting it in
    257                            buffer[count] = ch;
    258                            count--;
    259                            buffer[count] = (char) (55296 + random.nextInt(128));
    260                        }
    261                    } else if(ch >= 55296 && ch <= 56191) {
    262                        if(count == 0) {
    263                            count++;
    264                        } else {
    265                            // high surrogate, insert low surrogate before putting it in
    266                            buffer[count] = (char) (56320 + random.nextInt(128));
    267                            count--;
    268                            buffer[count] = ch;
    269                        }
    270                    } else if(ch >= 56192 && ch <= 56319) {
    271                        // private high surrogate, no effing clue, so skip it
    272                        count++;
    273                    } else {
    274                        buffer[count] = ch;
    275                    }
    276                } else {
    277                    count++;
    278                }
    279            }
    280            return new String(buffer);
    281        }
    282
    283        /**
    284         * <p>Creates a random string whose length is the number of characters
    285         * specified.</p>
    286         *
    287         * <p>Characters will be chosen from the set of characters
    288         * specified.</p>
    289         *
    290         * @param count  the length of random string to create
    291         * @param chars  the String containing the set of characters to use,
    292         *  may be null
    293         * @return the random string
    294         * @throws IllegalArgumentException if {@code count} &lt; 0.
    295         */
    296        public static String random(int count, String chars) {
    297            if (chars == null) {
    298                return random(count, 0, 0, false, false, null, RANDOM);
    299            }
    300            return random(count, chars.toCharArray());
    301        }
    302
    303        /**
    304         * <p>Creates a random string whose length is the number of characters
    305         * specified.</p>
    306         *
    307         * <p>Characters will be chosen from the set of characters specified.</p>
    308         *
    309         * @param count  the length of random string to create
    310         * @param chars  the character array containing the set of characters to use,
    311         *  may be null
    312         * @return the random string
    313         * @throws IllegalArgumentException if {@code count} &lt; 0.
    314         */
    315        public static String random(int count, char... chars) {
    316            if (chars == null) {
    317                return random(count, 0, 0, false, false, null, RANDOM);
    318            }
    319            return random(count, 0, chars.length, false, false, chars, RANDOM);
    320        }
    321
    322    }