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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3;

import java.util.Random;

/**
 * 

Operations for random {@code String}s.

*

Currently private high surrogate characters are ignored. * These are Unicode characters that fall between the values 56192 (db80) * and 56319 (dbff) as 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 (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 surrogate.

*

RandomStringUtils is intended for simple use cases. For more advanced * use cases consider using commons-text * * RandomStringGenerator instead.

* *

#ThreadSafe#

* @since 1.0 */ public class RandomStringUtils { /** *

Random object used by random method. This has to be not local * to the random method so as to not return the same value in the * same millisecond.

*/ private static final Random RANDOM = new Random(); /** *

{@code RandomStringUtils} instances should NOT be constructed in * standard programming. Instead, the class should be used as * {@code RandomStringUtils.random(5);}.

* *

This constructor is public to permit tools that require a JavaBean instance * to operate.

*/ public RandomStringUtils() { super(); } // Random //----------------------------------------------------------------------- /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of all characters.

* * @param count the length of random string to create * @return the random string */ public static String random(final int count) { return random(count, false, false); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of characters whose * ASCII value is between {@code 32} and {@code 126} (inclusive).

* * @param count the length of random string to create * @return the random string */ public static String randomAscii(final int count) { return random(count, 32, 127, false, false); } /** *

Creates a random string whose length is between the inclusive minimum and * the exclusive maximum.

* *

Characters will be chosen from the set of characters whose * ASCII value is between {@code 32} and {@code 126} (inclusive).

* * @param minLengthInclusive the inclusive minimum length of the string to generate * @param maxLengthExclusive the exclusive maximum length of the string to generate * @return the random string * @since 3.5 */ public static String randomAscii(final int minLengthInclusive, final int maxLengthExclusive) { return randomAscii(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive)); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of Latin alphabetic * characters (a-z, A-Z).

* * @param count the length of random string to create * @return the random string */ public static String randomAlphabetic(final int count) { return random(count, true, false); } /** *

Creates a random string whose length is between the inclusive minimum and * the exclusive maximum.

* *

Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z).

* * @param minLengthInclusive the inclusive minimum length of the string to generate * @param maxLengthExclusive the exclusive maximum length of the string to generate * @return the random string * @since 3.5 */ public static String randomAlphabetic(final int minLengthInclusive, final int maxLengthExclusive) { return randomAlphabetic(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive)); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of Latin alphabetic * characters (a-z, A-Z) and the digits 0-9.

* * @param count the length of random string to create * @return the random string */ public static String randomAlphanumeric(final int count) { return random(count, true, true); } /** *

Creates a random string whose length is between the inclusive minimum and * the exclusive maximum.

* *

Characters will be chosen from the set of Latin alphabetic * characters (a-z, A-Z) and the digits 0-9.

* * @param minLengthInclusive the inclusive minimum length of the string to generate * @param maxLengthExclusive the exclusive maximum length of the string to generate * @return the random string * @since 3.5 */ public static String randomAlphanumeric(final int minLengthInclusive, final int maxLengthExclusive) { return randomAlphanumeric(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive)); } /** *

Creates a random string whose length is the number of characters specified.

* *

Characters will be chosen from the set of characters which match the POSIX [:graph:] * regular expression character class. This class contains all visible ASCII characters * (i.e. anything except spaces and control characters).

* * @param count the length of random string to create * @return the random string * @since 3.5 */ public static String randomGraph(final int count) { return random(count, 33, 126, false, false); } /** *

Creates a random string whose length is between the inclusive minimum and * the exclusive maximum.

* *

Characters will be chosen from the set of \p{Graph} characters.

* * @param minLengthInclusive the inclusive minimum length of the string to generate * @param maxLengthExclusive the exclusive maximum length of the string to generate * @return the random string * @since 3.5 */ public static String randomGraph(final int minLengthInclusive, final int maxLengthExclusive) { return randomGraph(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive)); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of numeric * characters.

* * @param count the length of random string to create * @return the random string */ public static String randomNumeric(final int count) { return random(count, false, true); } /** *

Creates a random string whose length is between the inclusive minimum and * the exclusive maximum.

* *

Characters will be chosen from the set of \p{Digit} characters.

* * @param minLengthInclusive the inclusive minimum length of the string to generate * @param maxLengthExclusive the exclusive maximum length of the string to generate * @return the random string * @since 3.5 */ public static String randomNumeric(final int minLengthInclusive, final int maxLengthExclusive) { return randomNumeric(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive)); } /** *

Creates a random string whose length is the number of characters specified.

* *

Characters will be chosen from the set of characters which match the POSIX [:print:] * regular expression character class. This class includes all visible ASCII characters and spaces * (i.e. anything except control characters).

* * @param count the length of random string to create * @return the random string * @since 3.5 */ public static String randomPrint(final int count) { return random(count, 32, 126, false, false); } /** *

Creates a random string whose length is between the inclusive minimum and * the exclusive maximum.

* *

Characters will be chosen from the set of \p{Print} characters.

* * @param minLengthInclusive the inclusive minimum length of the string to generate * @param maxLengthExclusive the exclusive maximum length of the string to generate * @return the random string * @since 3.5 */ public static String randomPrint(final int minLengthInclusive, final int maxLengthExclusive) { return randomPrint(RandomUtils.nextInt(minLengthInclusive, maxLengthExclusive)); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of alpha-numeric * characters as indicated by the arguments.

* * @param count the length of random string to create * @param letters if {@code true}, generated string may include * alphabetic characters * @param numbers if {@code true}, generated string may include * numeric characters * @return the random string */ public static String random(final int count, final boolean letters, final boolean numbers) { return random(count, 0, 0, letters, numbers); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of alpha-numeric * characters as indicated by the arguments.

* * @param count the length of random string to create * @param start the position in set of chars to start at * @param end the position in set of chars to end before * @param letters if {@code true}, generated string may include * alphabetic characters * @param numbers if {@code true}, generated string may include * numeric characters * @return the random string */ public static String random(final int count, final int start, final int end, final boolean letters, final boolean numbers) { return random(count, start, end, letters, numbers, null, RANDOM); } /** *

Creates a random string based on a variety of options, using * default source of randomness.

* *

This method has exactly the same semantics as * {@link #random(int,int,int,boolean,boolean,char[],Random)}, but * instead of using an externally supplied source of randomness, it uses * the internal static {@link Random} instance.

* * @param count the length of random string to create * @param start the position in set of chars to start at * @param end the position in set of chars to end before * @param letters only allow letters? * @param numbers only allow numbers? * @param chars the set of chars to choose randoms from. * If {@code null}, then it will use the set of all chars. * @return the random string * @throws ArrayIndexOutOfBoundsException if there are not * {@code (end - start) + 1} characters in the set array. */ public static String random(final int count, final int start, final int end, final boolean letters, final boolean numbers, final char... chars) { return random(count, start, end, letters, numbers, chars, RANDOM); } /** *

Creates a random string based on a variety of options, using * supplied source of randomness.

* *

If start and end are both {@code 0}, start and end are set * to {@code ' '} and {@code 'z'}, the ASCII printable * characters, will be used, unless letters and numbers are both * {@code false}, in which case, start and end are set to * {@code 0} and {@link Character#MAX_CODE_POINT}. * *

If set is not {@code null}, characters between start and * end are chosen.

* *

This method accepts a user-supplied {@link Random} * instance to use as a source of randomness. By seeding a single * {@link Random} instance with a fixed seed and using it for each call, * the same random sequence of strings can be generated repeatedly * and predictably.

* * @param count the length of random string to create * @param start the position in set of chars to start at (inclusive) * @param end the position in set of chars to end before (exclusive) * @param letters only allow letters? * @param numbers only allow numbers? * @param chars the set of chars to choose randoms from, must not be empty. * If {@code null}, then it will use the set of all chars. * @param random a source of randomness. * @return the random string * @throws ArrayIndexOutOfBoundsException if there are not * {@code (end - start) + 1} characters in the set array. * @throws IllegalArgumentException if {@code count} < 0 or the provided chars array is empty. * @since 2.0 */ public static String random(int count, int start, int end, final boolean letters, final boolean numbers, final char[] chars, final Random random) { if (count == 0) { return StringUtils.EMPTY; } else if (count < 0) { throw new IllegalArgumentException("Requested random string length " + count + " is less than 0."); } if (chars != null && chars.length == 0) { throw new IllegalArgumentException("The chars array must not be empty"); } if (start == 0 && end == 0) { if (chars != null) { end = chars.length; } else { if (!letters && !numbers) { end = Character.MAX_CODE_POINT; } else { end = 'z' + 1; start = ' '; } } } else { if (end <= start) { throw new IllegalArgumentException("Parameter end (" + end + ") must be greater than start (" + start + ")"); } } final int zero_digit_ascii = 48; final int first_letter_ascii = 65; if (chars == null && (numbers && end <= zero_digit_ascii || letters && end <= first_letter_ascii)) { throw new IllegalArgumentException("Parameter end (" + end + ") must be greater then (" + zero_digit_ascii + ") for generating digits " + "or greater then (" + first_letter_ascii + ") for generating letters."); } final StringBuilder builder = new StringBuilder(count); final int gap = end - start; while (count-- != 0) { int codePoint; if (chars == null) { codePoint = random.nextInt(gap) + start; switch (Character.getType(codePoint)) { case Character.UNASSIGNED: case Character.PRIVATE_USE: case Character.SURROGATE: count++; continue; } } else { codePoint = chars[random.nextInt(gap) + start]; } final int numberOfChars = Character.charCount(codePoint); if (count == 0 && numberOfChars > 1) { count++; continue; } if (letters && Character.isLetter(codePoint) || numbers && Character.isDigit(codePoint) || !letters && !numbers) { builder.appendCodePoint(codePoint); if (numberOfChars == 2) { count--; } } else { count++; } } return builder.toString(); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of characters * specified by the string, must not be empty. * If null, the set of all characters is used.

* * @param count the length of random string to create * @param chars the String containing the set of characters to use, * may be null, but must not be empty * @return the random string * @throws IllegalArgumentException if {@code count} < 0 or the string is empty. */ public static String random(final int count, final String chars) { if (chars == null) { return random(count, 0, 0, false, false, null, RANDOM); } return random(count, chars.toCharArray()); } /** *

Creates a random string whose length is the number of characters * specified.

* *

Characters will be chosen from the set of characters specified.

* * @param count the length of random string to create * @param chars the character array containing the set of characters to use, * may be null * @return the random string * @throws IllegalArgumentException if {@code count} < 0. */ public static String random(final int count, final char... chars) { if (chars == null) { return random(count, 0, 0, false, false, null, RANDOM); } return random(count, 0, chars.length, false, false, chars, RANDOM); } }




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