RandomStringUtils.java
/*
* 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.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;
import org.apache.commons.lang3.exception.UncheckedException;
/**
* Generates random {@link String}s.
* <p>
* Starting in version 3.15.0, this classes uses {@link SecureRandom#getInstanceStrong()}.
* </p>
* <p>
* Before version 3.15.0, this classes used {@link ThreadLocalRandom#current()}, which was NOT cryptographically secure.
* </p>
* <p>
* RandomStringUtils is intended for simple use cases. For more advanced use cases consider using Apache Commons Text's
* <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/RandomStringGenerator.html"> RandomStringGenerator</a>
* instead.
* </p>
* <p>
* The Apache Commons project provides <a href="https://commons.apache.org/proper/commons-rng/">Commons RNG</a> dedicated to pseudo-random number generation,
* that may be a better choice for applications with more stringent requirements (performance and/or correctness).
* </p>
* <p>
* 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
* 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.
* </p>
* <p>
* #ThreadSafe#
* </p>
*
* @since 1.0
*/
public class RandomStringUtils {
private static final ThreadLocal<SecureRandom> RANDOM = ThreadLocal.withInitial(() -> {
try {
return SecureRandom.getInstanceStrong();
} catch (NoSuchAlgorithmException e) {
throw new UncheckedException(e);
}
});
static SecureRandom random() {
return RANDOM.get();
}
private static final char[] ALPHANUMERICAL_CHARS = {
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
};
/**
* Creates a random string whose length is the number of characters
* specified.
*
* <p>Characters will be chosen from the set of all characters.</p>
*
* @param count the length of random string to create
* @return the random string
* @throws IllegalArgumentException if {@code count} < 0.
*/
public static String random(final int count) {
return random(count, false, false);
}
/**
* Creates a random string whose length is the number of characters
* specified.
*
* <p>Characters will be chosen from the set of alpha-numeric
* characters as indicated by the arguments.</p>
*
* @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
* @throws IllegalArgumentException if {@code count} < 0.
*/
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.
*
* <p>Characters will be chosen from the set of characters specified.</p>
*
* @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());
}
/**
* Creates a random string whose length is the number of characters
* specified.
*
* <p>Characters will be chosen from the set of alpha-numeric
* characters as indicated by the arguments.</p>
*
* @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
* @throws IllegalArgumentException if {@code count} < 0.
*/
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.
*
* <p>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.</p>
*
* @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
* @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.
* @throws IllegalArgumentException if {@code count} < 0.
*/
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.
*
* <p>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}.
*
* <p>If set is not {@code null}, characters between start and
* end are chosen.</p>
*
* <p>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.</p>
*
* @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 if {@code true}, generated string may include
* alphabetic characters
* @param numbers if {@code true}, generated string may include
* numeric characters
* @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;
}
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 + ")");
}
if (end > Character.MAX_CODE_POINT) {
// Technically, it should be `Character.MAX_CODE_POINT+1` as `end` is excluded
// But the character `Character.MAX_CODE_POINT` is private use, so it would anyway be excluded
end = Character.MAX_CODE_POINT;
}
// Optimize generation of full alphanumerical characters
// Normally, we would need to pick a 7-bit integer, since gap = 'z' - '0' + 1 = 75 > 64
// In turn, this would make us reject the sampling with probability 1 - 62 / 2^7 > 1 / 2
// Instead we can pick directly from the right set of 62 characters, which requires
// picking a 6-bit integer and only rejecting with probability 2 / 64 = 1 / 32
if (chars == null && letters && numbers && start <= '0' && end >= 'z' + 1) {
return random(count, 0, 0, false, false, ALPHANUMERICAL_CHARS, random);
}
// Optimize start and end when filtering by letters and/or numbers:
// The range provided may be too large since we filter anyway afterward.
// Note the use of Math.min/max (as opposed to setting start to '0' for example),
// since it is possible the range start/end excludes some of the letters/numbers,
// e.g., it is possible that start already is '1' when numbers = true, and start
// needs to stay equal to '1' in that case.
if (chars == null) {
if (letters && numbers) {
start = Math.max('0', start);
end = Math.min('z' + 1, end);
} else if (numbers) {
// just numbers, no letters
start = Math.max('0', start);
end = Math.min('9' + 1, end);
} else if (letters) {
// just letters, no numbers
start = Math.max('A', start);
end = Math.min('z' + 1, end);
}
}
final int zeroDigitAscii = 48;
final int firstLetterAscii = 65;
if (chars == null && (numbers && end <= zeroDigitAscii
|| letters && end <= firstLetterAscii)) {
throw new IllegalArgumentException("Parameter end (" + end + ") must be greater then (" + zeroDigitAscii + ") for generating digits " +
"or greater then (" + firstLetterAscii + ") for generating letters.");
}
final StringBuilder builder = new StringBuilder(count);
final int gap = end - start;
final int gapBits = Integer.SIZE - Integer.numberOfLeadingZeros(gap);
// The size of the cache we use is an heuristic:
// about twice the number of bytes required if no rejection
// Ideally the cache size depends on multiple factor, including the cost of generating x bytes
// of randomness as well as the probability of rejection. It is however not easy to know
// those values programmatically for the general case.
final CachedRandomBits arb = new CachedRandomBits((count * gapBits + 3) / 5 + 10, random);
while (count-- != 0) {
// Generate a random value between start (included) and end (excluded)
final int randomValue = arb.nextBits(gapBits) + start;
// Rejection sampling if value too large
if (randomValue >= end) {
count++;
continue;
}
final int codePoint;
if (chars == null) {
codePoint = randomValue;
switch (Character.getType(codePoint)) {
case Character.UNASSIGNED:
case Character.PRIVATE_USE:
case Character.SURROGATE:
count++;
continue;
}
} else {
codePoint = chars[randomValue];
}
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.
*
* <p>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.</p>
*
* @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.
*
* <p>Characters will be chosen from the set of Latin alphabetic
* characters (a-z, A-Z).</p>
*
* @param count the length of random string to create
* @return the random string
* @throws IllegalArgumentException if {@code count} < 0.
*/
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.
*
* <p>Characters will be chosen from the set of Latin alphabetic characters (a-z, A-Z).</p>
*
* @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.
*
* <p>Characters will be chosen from the set of Latin alphabetic
* characters (a-z, A-Z) and the digits 0-9.</p>
*
* @param count the length of random string to create
* @return the random string
* @throws IllegalArgumentException if {@code count} < 0.
*/
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.
*
* <p>Characters will be chosen from the set of Latin alphabetic
* characters (a-z, A-Z) and the digits 0-9.</p>
*
* @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.
*
* <p>Characters will be chosen from the set of characters whose
* ASCII value is between {@code 32} and {@code 126} (inclusive).</p>
*
* @param count the length of random string to create
* @return the random string
* @throws IllegalArgumentException if {@code count} < 0.
*/
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.
*
* <p>Characters will be chosen from the set of characters whose
* ASCII value is between {@code 32} and {@code 126} (inclusive).</p>
*
* @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.
*
* <p>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).</p>
*
* @param count the length of random string to create
* @return the random string
* @throws IllegalArgumentException if {@code count} < 0.
* @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.
*
* <p>Characters will be chosen from the set of \p{Graph} characters.</p>
*
* @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.
*
* <p>Characters will be chosen from the set of numeric
* characters.</p>
*
* @param count the length of random string to create
* @return the random string
* @throws IllegalArgumentException if {@code count} < 0.
*/
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.
*
* <p>Characters will be chosen from the set of \p{Digit} characters.</p>
*
* @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.
*
* <p>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).</p>
*
* @param count the length of random string to create
* @return the random string
* @throws IllegalArgumentException if {@code count} < 0.
* @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.
*
* <p>Characters will be chosen from the set of \p{Print} characters.</p>
*
* @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));
}
/**
* {@link RandomStringUtils} instances should NOT be constructed in
* standard programming. Instead, the class should be used as
* {@code RandomStringUtils.random(5);}.
*
* <p>This constructor is public to permit tools that require a JavaBean instance
* to operate.</p>
*
* @deprecated TODO Make private in 4.0.
*/
@Deprecated
public RandomStringUtils() {
// empty
}
}