Package org.apache.commons.lang3

Class RandomStringUtils

  • public class RandomStringUtils
extends Object

    Generates random Strings.

    Caveat: Instances of Random, upon which the implementation of this class relies, are 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#

    Since:
    1.0

    • Constructor Summary

      Constructors 
      Constructor Description
      RandomStringUtils()
      RandomStringUtils instances should NOT be constructed in standard programming.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static String random​(int count)
      Creates a random string whose length is the number of characters specified.
      static String random​(int count, boolean letters, boolean numbers)
      Creates a random string whose length is the number of characters specified.
      static String random​(int count, char... chars)
      Creates a random string whose length is the number of characters specified.
      static String random​(int count, int start, int end, boolean letters, boolean numbers)
      Creates a random string whose length is the number of characters specified.
      static String random​(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.
      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.
      static String random​(int count, String chars)
      Creates a random string whose length is the number of characters specified.
      static String randomAlphabetic​(int count)
      Creates a random string whose length is the number of characters specified.
      static String randomAlphabetic​(int minLengthInclusive, int maxLengthExclusive)
      Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
      static String randomAlphanumeric​(int count)
      Creates a random string whose length is the number of characters specified.
      static String randomAlphanumeric​(int minLengthInclusive, int maxLengthExclusive)
      Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
      static String randomAscii​(int count)
      Creates a random string whose length is the number of characters specified.
      static String randomAscii​(int minLengthInclusive, int maxLengthExclusive)
      Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
      static String randomGraph​(int count)
      Creates a random string whose length is the number of characters specified.
      static String randomGraph​(int minLengthInclusive, int maxLengthExclusive)
      Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
      static String randomNumeric​(int count)
      Creates a random string whose length is the number of characters specified.
      static String randomNumeric​(int minLengthInclusive, int maxLengthExclusive)
      Creates a random string whose length is between the inclusive minimum and the exclusive maximum.
      static String randomPrint​(int count)
      Creates a random string whose length is the number of characters specified.
      static String randomPrint​(int minLengthInclusive, int maxLengthExclusive)
      Creates a random string whose length is between the inclusive minimum and the exclusive maximum.

    • Constructor Detail

      • RandomStringUtils

        public RandomStringUtils()

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

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

    • Method Detail

      • random

        public static String random​(int count)

        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

      • randomAscii

        public static String randomAscii​(int count)

        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 32 and 126 (inclusive).

        Parameters:
        count - the length of random string to create
        Returns:
        the random string

      • randomAscii

        public static String randomAscii​(int minLengthInclusive,
                                 int maxLengthExclusive)

        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 32 and 126 (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

      • randomAlphabetic

        public static String randomAlphabetic​(int count)

        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

      • randomAlphabetic

        public static String randomAlphabetic​(int minLengthInclusive,
                                      int maxLengthExclusive)

        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

      • randomAlphanumeric

        public static String randomAlphanumeric​(int count)

        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

      • randomAlphanumeric

        public static String randomAlphanumeric​(int minLengthInclusive,
                                        int maxLengthExclusive)

        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

      • randomGraph

        public static String randomGraph​(int count)

        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
        Since:
        3.5

      • randomGraph

        public static String randomGraph​(int minLengthInclusive,
                                 int maxLengthExclusive)

        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

      • randomNumeric

        public static String randomNumeric​(int count)

        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

      • randomNumeric

        public static String randomNumeric​(int minLengthInclusive,
                                   int maxLengthExclusive)

        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

      • randomPrint

        public static String randomPrint​(int count)

        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
        Since:
        3.5

      • randomPrint

        public static String randomPrint​(int minLengthInclusive,
                                 int maxLengthExclusive)

        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

      • random

        public static String random​(int count,
                            boolean letters,
                            boolean 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.

        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

      • random

        public static String random​(int count,
                            int start,
                            int end,
                            boolean letters,
                            boolean 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.

        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

      • random

        public static String random​(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.

        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 static Random instance.

        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) + 1 characters in the set array.

      • random

        public 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 both false, in which case, start and end are set to 0 and Character.MAX_CODE_POINT.

        If set is not null, characters between start and end are chosen.

        This method accepts a user-supplied Random instance to use as a source of randomness. By seeding a single Random instance 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) + 1 characters in the set array.
        IllegalArgumentException - if count < 0 or the provided chars array is empty.
        Since:
        2.0

      • random

        public static String random​(int count,
                            String chars)

        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.

      • random

        public static String random​(int count,
                            char... chars)

        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.