org.apache.commons.lang3

Class RandomStringUtils

java.lang.Object

org.apache.commons.lang3.RandomStringUtils

public class RandomStringUtils
extends Object

Operations for random Strings.

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.

Caveat: Instances of Random, upon which the implementation of this class relies, are not cryptographically secure.

Please note that the Apache Commons project provides a component dedicated to pseudo-random number generation, namely Commons RNG, that may be a better choice for applications with more stringent requirements (performance and/or correctness).

#ThreadSafe#

Since:

1.0

Constructor Summary

Constructors

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

Method Summary

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	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.

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

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 - 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 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 - 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.