Class RandomStringUtils
Strings.
 
 Use secure() to get the singleton instance based on SecureRandom() which uses a secure random number generator implementing the
 default random number algorithm.
 
 Use secureStrong() to get the singleton instance based on SecureRandom.getInstanceStrong() which uses an instance that was selected by using
 the algorithms/providers specified in the securerandom.strongAlgorithms Security property.
 
 Use insecure() to get the singleton instance based on ThreadLocalRandom.current() which is not cryptographically secure. In addition,
 instances do not use a cryptographically random seed unless the system property java.util.secureRandomSeed is set to
 true.
 
 Starting in version 3.17.0, the method secure() uses SecureRandom() instead of SecureRandom.getInstanceStrong(), and
 adds secureStrong().
 
 Starting in version 3.16.0, this class uses secure() for static methods and adds insecure().
 
 Starting in version 3.15.0, this class uses SecureRandom.getInstanceStrong() for static methods.
 
 Before version 3.15.0, this class used ThreadLocalRandom.current() for static methods, which is not cryptographically secure.
 
RandomStringUtils is intended for simple use cases. For more advanced use cases consider using Apache Commons Text's RandomStringGenerator instead.
The Apache Commons project provides Commons RNG dedicated to pseudo-random number generation, that may be a better choice for applications with more stringent requirements (performance and/or correctness).
Note that 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.
#ThreadSafe#
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Constructor SummaryConstructors
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Method SummaryModifier and TypeMethodDescriptionstatic RandomStringUtilsinsecure()Gets the singleton instance based onThreadLocalRandom.current(); which is not cryptographically secure; usesecure()to use an algorithms/providers specified in thesecurerandom.strongAlgorithmsSecurityproperty.next(int count) Creates a random string whose length is the number of characters specified.next(int count, boolean letters, boolean numbers) Creates a random string whose length is the number of characters specified.next(int count, char... chars) Creates a random string whose length is the number of characters specified.next(int count, int start, int end, boolean letters, boolean numbers) Creates a random string whose length is the number of characters specified.next(int count, int start, int end, boolean letters, boolean numbers, char... chars) Creates a random string based on a variety of options, using default source of randomness.Creates a random string whose length is the number of characters specified.nextAlphabetic(int count) Creates a random string whose length is the number of characters specified.nextAlphabetic(int minLengthInclusive, int maxLengthExclusive) Creates a random string whose length is between the inclusive minimum and the exclusive maximum.nextAlphanumeric(int count) Creates a random string whose length is the number of characters specified.nextAlphanumeric(int minLengthInclusive, int maxLengthExclusive) Creates a random string whose length is between the inclusive minimum and the exclusive maximum.nextAscii(int count) Creates a random string whose length is the number of characters specified.nextAscii(int minLengthInclusive, int maxLengthExclusive) Creates a random string whose length is between the inclusive minimum and the exclusive maximum.nextGraph(int count) Creates a random string whose length is the number of characters specified.nextGraph(int minLengthInclusive, int maxLengthExclusive) Creates a random string whose length is between the inclusive minimum and the exclusive maximum.nextNumeric(int count) Creates a random string whose length is the number of characters specified.nextNumeric(int minLengthInclusive, int maxLengthExclusive) Creates a random string whose length is between the inclusive minimum and the exclusive maximum.nextPrint(int count) Creates a random string whose length is the number of characters specified.nextPrint(int minLengthInclusive, int maxLengthExclusive) Creates a random string whose length is between the inclusive minimum and the exclusive maximum.static Stringrandom(int count) Deprecated.static Stringrandom(int count, boolean letters, boolean numbers) Deprecated.static Stringrandom(int count, char... chars) Deprecated.static Stringrandom(int count, int start, int end, boolean letters, boolean numbers) Deprecated.static Stringrandom(int count, int start, int end, boolean letters, boolean numbers, char... chars) Deprecated.static Stringrandom(int count, int start, int end, boolean letters, boolean numbers, char[] chars, Random random) Creates a random string based on a variety of options, using supplied source of randomness.static StringDeprecated.static StringrandomAlphabetic(int count) Deprecated.static StringrandomAlphabetic(int minLengthInclusive, int maxLengthExclusive) Deprecated.static StringrandomAlphanumeric(int count) Deprecated.static StringrandomAlphanumeric(int minLengthInclusive, int maxLengthExclusive) Deprecated.static StringrandomAscii(int count) Deprecated.static StringrandomAscii(int minLengthInclusive, int maxLengthExclusive) Deprecated.static StringrandomGraph(int count) Deprecated.static StringrandomGraph(int minLengthInclusive, int maxLengthExclusive) Deprecated.static StringrandomNumeric(int count) Deprecated.static StringrandomNumeric(int minLengthInclusive, int maxLengthExclusive) Deprecated.static StringrandomPrint(int count) Deprecated.static StringrandomPrint(int minLengthInclusive, int maxLengthExclusive) Deprecated.static RandomStringUtilssecure()Gets the singleton instance based onSecureRandom()which uses a secure random number generator (RNG) implementing the default random number algorithm.static RandomStringUtilsGets the singleton instance based onSecureRandom.getInstanceStrong()which uses an algorithms/providers specified in thesecurerandom.strongAlgorithmsSecurityproperty.toString()
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Constructor Details- 
RandomStringUtilsDeprecated.TODO Make private in 4.0.RandomStringUtilsinstances should NOT be constructed in standard programming. Instead, the class should be used asRandomStringUtils.random(5);.This constructor is public to permit tools that require a JavaBean instance to operate. 
 
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Method Details- 
insecureGets the singleton instance based onThreadLocalRandom.current(); which is not cryptographically secure; usesecure()to use an algorithms/providers specified in thesecurerandom.strongAlgorithmsSecurityproperty.The method ThreadLocalRandom.current()is called on-demand.- Returns:
- the singleton instance based on ThreadLocalRandom.current().
- Since:
- 3.16.0
- See Also:
 
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randomDeprecated.Creates a random string whose length is the number of characters specified.Characters will be chosen from the set of all characters. - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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randomDeprecated.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. - Parameters:
- count- the length of random string to create
- letters- if- true, generated string may include alphabetic characters
- numbers- if- true, generated string may include numeric characters
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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randomDeprecated.Creates a random string whose length is the number of characters specified.Characters will be chosen from the set of characters specified. - Parameters:
- count- the length of random string to create
- chars- the character array containing the set of characters to use, may be null
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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random@Deprecated public static String random(int count, int start, int end, boolean letters, boolean numbers) Deprecated.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. - Parameters:
- count- the length of random string to create
- start- the position in set of chars to start at
- end- the position in set of chars to end before
- letters- if- true, generated string may include alphabetic characters
- numbers- if- true, generated string may include numeric characters
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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random@Deprecated public static String random(int count, int start, int end, boolean letters, boolean numbers, char... chars) Deprecated.Creates a random string based on a variety of options, using default source of randomness.This method has exactly the same semantics as random(int,int,int,boolean,boolean,char[],Random), but instead of using an externally supplied source of randomness, it uses the internal staticRandominstance.- Parameters:
- count- the length of random string to create
- start- the position in set of chars to start at
- end- the position in set of chars to end before
- letters- if- true, generated string may include alphabetic characters
- numbers- if- true, generated string may include numeric characters
- chars- the set of chars to choose randoms from. If- null, then it will use the set of all chars.
- Returns:
- the random string
- Throws:
- ArrayIndexOutOfBoundsException- if there are not- (end - start) + 1characters in the set array.
- IllegalArgumentException- if- count< 0.
 
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randompublic static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars, Random random) Creates a random string based on a variety of options, using supplied source of randomness.If start and end are both 0, start and end are set to' 'and'z', the ASCII printable characters, will be used, unless letters and numbers are bothfalse, in which case, start and end are set to0andCharacter.MAX_CODE_POINT.If set is not null, characters between start and end are chosen.This method accepts a user-supplied Randominstance to use as a source of randomness. By seeding a singleRandominstance with a fixed seed and using it for each call, the same random sequence of strings can be generated repeatedly and predictably.- Parameters:
- count- the length of random string to create
- start- the position in set of chars to start at (inclusive)
- end- the position in set of chars to end before (exclusive)
- letters- if- true, generated string may include alphabetic characters
- numbers- if- true, generated string may include numeric characters
- chars- the set of chars to choose randoms from, must not be empty. If- null, then it will use the set of all chars.
- random- a source of randomness.
- Returns:
- the random string
- Throws:
- ArrayIndexOutOfBoundsException- if there are not- (end - start) + 1characters in the set array.
- IllegalArgumentException- if- count< 0 or the provided chars array is empty.
- Since:
- 2.0
 
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randomDeprecated.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. - Parameters:
- count- the length of random string to create
- chars- the String containing the set of characters to use, may be null, but must not be empty
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0 or the string is empty.
 
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randomAlphabeticDeprecated.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). - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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randomAlphabeticDeprecated.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). - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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randomAlphanumericDeprecated.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. - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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randomAlphanumericDeprecated.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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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randomAsciiDeprecated.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 32and126(inclusive).- Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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randomAsciiDeprecated.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 32and126(inclusive).- Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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randomGraphDeprecated.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). - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.5
 
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randomGraphDeprecated.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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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randomNumericDeprecated.Creates a random string whose length is the number of characters specified.Characters will be chosen from the set of numeric characters. - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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randomNumericDeprecated.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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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randomPrintDeprecated.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). - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.5
 
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randomPrintDeprecated.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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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secureGets the singleton instance based onSecureRandom()which uses a secure random number generator (RNG) implementing the default random number algorithm.The method SecureRandom()is called on-demand.- Returns:
- the singleton instance based on SecureRandom().
- Since:
- 3.16.0
- See Also:
 
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secureStrongGets the singleton instance based onSecureRandom.getInstanceStrong()which uses an algorithms/providers specified in thesecurerandom.strongAlgorithmsSecurityproperty.The method SecureRandom.getInstanceStrong()is called on-demand.- Returns:
- the singleton instance based on SecureRandom.getInstanceStrong().
- Since:
- 3.17.0
- See Also:
 
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nextCreates a random string whose length is the number of characters specified.Characters will be chosen from the set of all characters. - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.16.0
 
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nextCreates 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. - Parameters:
- count- the length of random string to create
- letters- if- true, generated string may include alphabetic characters
- numbers- if- true, generated string may include numeric characters
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.16.0
 
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nextCreates a random string whose length is the number of characters specified.Characters will be chosen from the set of characters specified. - Parameters:
- count- the length of random string to create
- chars- the character array containing the set of characters to use, may be null
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.16.0
 
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nextCreates 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. - Parameters:
- count- the length of random string to create
- start- the position in set of chars to start at
- end- the position in set of chars to end before
- letters- if- true, generated string may include alphabetic characters
- numbers- if- true, generated string may include numeric characters
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.16.0
 
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nextCreates a random string based on a variety of options, using default source of randomness.This method has exactly the same semantics as random(int,int,int,boolean,boolean,char[],Random), but instead of using an externally supplied source of randomness, it uses the internal staticRandominstance.- Parameters:
- count- the length of random string to create
- start- the position in set of chars to start at
- end- the position in set of chars to end before
- letters- if- true, generated string may include alphabetic characters
- numbers- if- true, generated string may include numeric characters
- chars- the set of chars to choose randoms from. If- null, then it will use the set of all chars.
- Returns:
- the random string
- Throws:
- ArrayIndexOutOfBoundsException- if there are not- (end - start) + 1characters in the set array.
- IllegalArgumentException- if- count< 0.
 
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nextCreates 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. - Parameters:
- count- the length of random string to create
- chars- the String containing the set of characters to use, may be null, but must not be empty
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0 or the string is empty.
- Since:
- 3.16.0
 
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nextAlphabeticCreates 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). - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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nextAlphabeticCreates 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). - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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nextAlphanumericCreates 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. - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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nextAlphanumericCreates 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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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nextAsciiCreates 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 32and126(inclusive).- Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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nextAsciiCreates 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 32and126(inclusive).- Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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nextGraphCreates 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). - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.5
 
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nextGraphCreates 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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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nextNumericCreates a random string whose length is the number of characters specified.Characters will be chosen from the set of numeric characters. - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
 
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nextNumericCreates 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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.5
 
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nextPrintCreates 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). - Parameters:
- count- the length of random string to create
- Returns:
- the random string
- Throws:
- IllegalArgumentException- if- count< 0.
- Since:
- 3.5, 3.16.0
 
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nextPrintCreates 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. - Parameters:
- minLengthInclusive- the inclusive minimum length of the string to generate
- maxLengthExclusive- the exclusive maximum length of the string to generate
- Returns:
- the random string
- Since:
- 3.16.0
 
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toString
 
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