org.apache.commons.lang3

## Class RandomStringUtils

- java.lang.Object
- - org.apache.commons.lang3.RandomStringUtils

-     public class RandomStringUtils
      extends Object

  Operations for random `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.

  #ThreadSafe#

  Since:
    1.0
  Version:
    $Id: RandomStringUtils.java 1532684 2013-10-16 08:28:42Z bayard $

- - ### Constructor Summary

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

  - ### Method Summary

    Methods
    Modifier and Type | Method and 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` | `randomAlphanumeric(int count)` Creates a random string whose length is the number of characters specified.
    `static String` | `randomAscii(int count)` Creates a random string whose length is the number of characters specified.
    `static String` | `randomNumeric(int count)` Creates a random string whose length is the number of characters specified.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### 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

    - #### 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 alphabetic characters.

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

    - #### 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 alpha-numeric characters.

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

    - #### 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

    - #### 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` - only allow letters?
        `numbers` - only allow numbers?
        `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 `Integer.MAX_VALUE`.

      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
        `end` - the position in set of chars to end before
        `letters` - only allow letters?
        `numbers` - only allow numbers?
        `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.

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