Package org.apache.commons.text

Class RandomStringGenerator.Builder

  • All Implemented Interfaces:
    Builder<RandomStringGenerator>
    Enclosing class:
    RandomStringGenerator
    public static class RandomStringGenerator.Builder
extends java.lang.Object
implements Builder<RandomStringGenerator>

    A builder for generating RandomStringGenerator instances.

    The behavior of a generator is controlled by properties set by this builder. Each property has a default value, which can be overridden by calling the methods defined in this class, prior to calling build().

    All the property setting methods return the Builder instance to allow for method chaining.

    The minimum and maximum code point values are defined using withinRange(int, int). The default values are 0 and Character.MAX_CODE_POINT respectively.

    The source of randomness can be set using usingRandom(TextRandomProvider), otherwise ThreadLocalRandom is used.

    The type of code points returned can be filtered using filteredBy(CharacterPredicate...), which defines a collection of tests that are applied to the randomly generated code points. The code points will only be included in the result if they pass at least one of the tests. Some commonly used predicates are provided by the CharacterPredicates enum.

    This class is not thread safe.

    Since:
    1.1

    • Field Detail

      • DEFAULT_MAXIMUM_CODE_POINT

        public static final int DEFAULT_MAXIMUM_CODE_POINT
        The default maximum code point allowed: Character.MAX_CODE_POINT (1114111).
        See Also:
        Constant Field Values

      • DEFAULT_LENGTH

        public static final int DEFAULT_LENGTH
        The default string length produced by this builder: 0.
        See Also:
        Constant Field Values

      • DEFAULT_MINIMUM_CODE_POINT

        public static final int DEFAULT_MINIMUM_CODE_POINT
        The default minimum code point allowed: 0.
        See Also:
        Constant Field Values

    • Constructor Detail

      • Builder

        public Builder()

    • Method Detail

      • withinRange

        public RandomStringGenerator.Builder withinRange​(int minimumCodePoint,
                                                 int maximumCodePoint)

        Specifies the minimum and maximum code points allowed in the generated string.

        Parameters:
        minimumCodePoint - the smallest code point allowed (inclusive)
        maximumCodePoint - the largest code point allowed (inclusive)
        Returns:
        this, to allow method chaining
        Throws:
        java.lang.IllegalArgumentException - if maximumCodePoint > Character.MAX_CODE_POINT
        java.lang.IllegalArgumentException - if minimumCodePoint < 0
        java.lang.IllegalArgumentException - if minimumCodePoint > maximumCodePoint

      • withinRange

        public RandomStringGenerator.Builder withinRange​(char[]... pairs)

        Specifies the array of minimum and maximum char allowed in the generated string.

        For example: 
         
     char [][] pairs = {{'0','9'}};
     char [][] pairs = {{'a','z'}};
     char [][] pairs = {{'a','z'},{'0','9'}};
        Parameters:
        pairs - array of characters array, expected is to pass min, max pairs through this arg.
        Returns:
        this, to allow method chaining.

      • filteredBy

        public RandomStringGenerator.Builder filteredBy​(CharacterPredicate... predicates)

        Limits the characters in the generated string to those that match at least one of the predicates supplied.

        Passing null or an empty array to this method will revert to the default behavior of allowing any character. Multiple calls to this method will replace the previously stored predicates.

        Parameters:
        predicates - the predicates, may be null or empty
        Returns:
        this, to allow method chaining

      • usingRandom

        public RandomStringGenerator.Builder usingRandom​(TextRandomProvider random)

        Overrides the default source of randomness. It is highly recommended that a random number generator library like Apache Commons RNG be used to provide the random number generation.

        When using Java 8 or later, TextRandomProvider is a functional interface and need not be explicitly implemented: 

         
     UniformRandomProvider rng = RandomSource.create(...);
     RandomStringGenerator gen = new RandomStringGenerator.Builder()
         .usingRandom(rng::nextInt)
         // additional builder calls as needed
         .build();

        Passing null to this method will revert to the default source of randomness.

        Parameters:
        random - the source of randomness, may be null
        Returns:
        this, to allow method chaining

      • selectFrom

        public RandomStringGenerator.Builder selectFrom​(char... chars)

        Limits the characters in the generated string to those who match at supplied list of Character.

        Passing null or an empty array to this method will revert to the default behavior of allowing any character. Multiple calls to this method will replace the previously stored Character.

        Parameters:
        chars - set of predefined Characters for random string generation the Character can be, may be null or empty
        Returns:
        this, to allow method chaining
        Since:
        1.2