Module java.base
Package java.util.random

Class RandomGeneratorFactory<T extends RandomGenerator>

java.lang.Object
java.util.random.RandomGeneratorFactory<T>
Type Parameters:
T - type of created random generator
public final class RandomGeneratorFactory<T extends RandomGenerator> extends Object
This is a factory class for generating multiple random number generators of a specific algorithm. RandomGeneratorFactory also provides methods for selecting random number generator algorithms. A specific RandomGeneratorFactory can be located by using the of(String) method, where the argument string is the name of the algorithm required. The method all() produces a non-empty Stream of all available RandomGeneratorFactorys that can be searched to locate a RandomGeneratorFactory suitable to the task. There are three methods for constructing a RandomGenerator instance, depending on the type of initial seed required. create(long) is used for long seed construction, create(byte[]) is used for byte[] seed construction, and create() is used for random seed construction. Example; 
   RandomGeneratorFactory<RandomGenerator> factory = RandomGeneratorFactory.of("Random");

    for (int i = 0; i < 10; i++) {
        new Thread(() -> {
            RandomGenerator random = factory.create(100L);
            System.out.println(random.nextDouble());
        }).start();
    }
RandomGeneratorFactory also provides methods describing the attributes (or properties) of a generator and can be used to select random number generator algorithms. These methods are typically used in conjunction with all(). In this example, the code locates the RandomGeneratorFactory that produces RandomGenerators with the highest number of state bits. 
    RandomGeneratorFactory<RandomGenerator> best = RandomGeneratorFactory.all()
        .filter(rgf -> !rgf.name().equals("SecureRandom")) // SecureRandom has MAX_VALUE stateBits.
        .sorted(Comparator.comparingInt(RandomGeneratorFactory<RandomGenerator>::stateBits).reversed())
        .findFirst()
        .orElse(RandomGeneratorFactory.of("Random"));
    System.out.println(best.name() + " in " + best.group() + " was selected");

    RandomGenerator rng = best.create();
    System.out.println(rng.nextLong());
Since:
17
See Also:

  • Method Details

    • of

      public static <T extends RandomGenerator> RandomGeneratorFactory<T> of(String name)
      Returns a RandomGeneratorFactory that can produce instances of RandomGenerator that utilize the name algorithm.
      Implementation Requirements:
      Availability is determined by RandomGeneratorFactory using the service provider API to locate implementations of the RandomGenerator interface.
      Type Parameters:
      T - Sub-interface of RandomGenerator to produce
      Parameters:
      name - Name of random number generator algorithm
      Returns:
      RandomGeneratorFactory of RandomGenerator
      Throws:
      NullPointerException - if name is null
      IllegalArgumentException - if the named algorithm is not found

    • getDefault

      public static RandomGeneratorFactory<RandomGenerator> getDefault()
      Returns a RandomGeneratorFactory meeting the minimal requirement of having an algorithm whose state bits are greater than or equal 64.
      Implementation Requirements:
      Since algorithms will improve over time, there is no guarantee that this method will return the same algorithm over time.
      Returns:
      a RandomGeneratorFactory

    • all

      public static Stream<RandomGeneratorFactory<RandomGenerator>> all()
      Returns a non-empty stream of available RandomGeneratorFactory(s). RandomGenerators that are marked as deprecated are not included in the result.
      Implementation Requirements:
      Availability is determined by RandomGeneratorFactory using the service provider API to locate implementations of the RandomGenerator interface.
      Returns:
      a non-empty stream of all available RandomGeneratorFactory(s).

    • name

      public String name()
      Return the name of the algorithm used by the random number generator.
      Returns:
      Name of the algorithm.

    • group

      public String group()
      Return the group name of the algorithm used by the random number generator.
      Returns:
      Group name of the algorithm.

    • stateBits

      public int stateBits()
      Returns number of bits used by the algorithm to maintain state of seed.
      Returns:
      number of bits used by the algorithm to maintain state of seed.

    • equidistribution

      public int equidistribution()
      Returns the equidistribution of the algorithm.
      Returns:
      the equidistribution of the algorithm.

    • period

      public BigInteger period()
      Return the period of the algorithm used by the random number generator. Returns BigInteger.ZERO if period is not determinable.
      Returns:
      BigInteger period.

    • isStatistical

      public boolean isStatistical()
      Return true if random generator is computed using an arithmetic algorithm and is statistically deterministic.
      Returns:
      true if random generator is statistical.

    • isStochastic

      public boolean isStochastic()
      Return true if random generator is computed using external or entropic sources as inputs.
      Returns:
      true if random generator is stochastic.

    • isHardware

      public boolean isHardware()
      Return true if random generator uses a hardware device (HRNG) to produce entropic input.
      Returns:
      true if random generator is generated by hardware.

    • isArbitrarilyJumpable

      public boolean isArbitrarilyJumpable()
      Return true if random generator can jump an arbitrarily specified distant point in the state cycle.
      Returns:
      true if random generator is arbitrarily jumpable.

    • isJumpable

      public boolean isJumpable()
      Return true if random generator can jump a specified distant point in the state cycle.
      Returns:
      true if random generator is jumpable.

    • isLeapable

      public boolean isLeapable()
      Return true if random generator is jumpable and can leap to a very distant point in the state cycle.
      Returns:
      true if random generator is leapable.

    • isSplittable

      public boolean isSplittable()
      Return true if random generator can be cloned into a separate object with the same properties but positioned further in the state cycle.
      Returns:
      true if random generator is splittable.

    • isStreamable

      public boolean isStreamable()
      Return true if random generator can be used to create Streams of random numbers.
      Returns:
      true if random generator is streamable.

    • isDeprecated

      public boolean isDeprecated()
      Return true if the implementation of RandomGenerator (algorithm) has been marked for deprecation.
      Implementation Note:
      Random number generator algorithms evolve over time; new algorithms will be introduced and old algorithms will lose standing. If an older algorithm is deemed unsuitable for continued use, it will be marked as deprecated to indicate that it may be removed at some point in the future.
      Returns:
      true if the implementation of RandomGenerator (algorithm) has been marked for deprecation

    • create

      public T create()
      Create an instance of RandomGenerator based on algorithm chosen.
      Returns:
      new in instance of RandomGenerator.

    • create

      public T create(long seed)
      Create an instance of RandomGenerator based on algorithm chosen providing a starting long seed. If long seed is not supported by an algorithm then the no argument form of create is used.
      Parameters:
      seed - long random seed value.
      Returns:
      new in instance of RandomGenerator.

    • create

      public T create(byte[] seed)
      Create an instance of RandomGenerator based on algorithm chosen providing a starting byte[] seed. If byte[] seed is not supported by an algorithm then the no argument form of create is used.
      Parameters:
      seed - byte array random seed value.
      Returns:
      new in instance of RandomGenerator.
      Throws:
      NullPointerException - if seed is null.