Package org.apache.commons.text

## Class RandomStringGenerator.Builder

- java.lang.Object
- - org.apache.commons.text.RandomStringGenerator.Builder

- All Implemented Interfaces:
    `Builder<RandomStringGenerator>`
  Enclosing class:
    RandomStringGenerator

      public static class RandomStringGenerator.Builder
      extends Object
      implements Builder<RandomStringGenerator>

  A builder for generating `RandomStringGenerator` instances.

  The behaviour 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 Summary

    Fields
    Modifier and Type | Field | Description
    --- | --- | ---
    `static int` | `DEFAULT_LENGTH` | The default string length produced by this builder: 0.
    `static int` | `DEFAULT_MAXIMUM_CODE_POINT` | The default maximum code point allowed: `Character.MAX_CODE_POINT` (1114111).
    `static int` | `DEFAULT_MINIMUM_CODE_POINT` | The default minimum code point allowed: 0.

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `Builder()` |

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `RandomStringGenerator` | `build()` | Builds the `RandomStringGenerator` using the properties specified.
    `RandomStringGenerator.Builder` | `filteredBy​(CharacterPredicate... predicates)` | Limits the characters in the generated string to those that match at least one of the predicates supplied.
    `RandomStringGenerator.Builder` | `selectFrom​(char... chars)` | Limits the characters in the generated string to those who match at supplied list of Character.
    `RandomStringGenerator.Builder` | `usingRandom​(TextRandomProvider random)` | Overrides the default source of randomness.
    `RandomStringGenerator.Builder` | `withinRange​(char[]... pairs)` | Specifies the array of minimum and maximum char allowed in the generated string.
    `RandomStringGenerator.Builder` | `withinRange​(int minimumCodePoint, int maximumCodePoint)` | Specifies the minimum and maximum code points allowed in the generated string.

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

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

- - ### 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:
        `IllegalArgumentException` - if `maximumCodePoint >` `Character.MAX_CODE_POINT`
        `IllegalArgumentException` - if `minimumCodePoint < 0`
        `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 behaviour 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 behaviour 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

    - #### build

          public RandomStringGenerator build()

      Builds the `RandomStringGenerator` using the properties specified.

      Specified by:
        `build` in interface `Builder<RandomStringGenerator>`
      Returns:
        the configured `RandomStringGenerator`