Module java.base
Package java.util

Class SplittableRandom

  • public final classSplittableRandomextendsObject
    A generator of uniform pseudorandom values applicable for use in (among other contexts) isolated parallel computations that may generate subtasks. ClassSplittableRandom supports methods for producing pseudorandom numbers of typeint,long, anddouble with similar usages as for classRandom but differs in the following ways:
    • Series of generated values pass the DieHarder suite testing independence and uniformity properties of random number generators. (Most recently validated with version 3.31.1.) These tests validate only the methods for certain types and ranges, but similar properties are expected to hold, at least approximately, for others as well. Theperiod (length of any series of generated values before it repeats) is at least 264.
    • Methodsplit() constructs and returns a new SplittableRandom instance that shares no mutable state with the current instance. However, with very high probability, the values collectively generated by the two objects have the same statistical properties as if the same quantity of values were generated by a single thread using a single SplittableRandom object.
    • Instances of SplittableRandom arenot thread-safe. They are designed to be split, not shared, across threads. For example, afork/join-style computation using random numbers might include a construction of the formnew Subtask(aSplittableRandom.split()).fork().
    • This class provides additional methods for generating random streams, that employ the above techniques when used in stream.parallel() mode.

    Instances ofSplittableRandom are not cryptographically secure. Consider instead usingSecureRandom in security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless thesystem propertyjava.util.secureRandomSeed is set totrue.

    Since:
    1.8

    • Constructor Summary

      Constructors 
      ConstructorDescription
      SplittableRandom()
      Creates a new SplittableRandom instance that is likely to generate sequences of values that are statistically independent of those of any other instances in the current program; and may, and typically does, vary across program invocations.
      SplittableRandom​(long seed)
      Creates a new SplittableRandom instance using the specified initial seed.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and TypeMethodDescription
      DoubleStreamdoubles()
      Returns an effectively unlimited stream of pseudorandom double values from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).
      DoubleStreamdoubles​(double randomNumberOrigin, double randomNumberBound)
      Returns an effectively unlimited stream of pseudorandom double values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      DoubleStreamdoubles​(long streamSize)
      Returns a stream producing the givenstreamSize number of pseudorandomdouble values from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).
      DoubleStreamdoubles​(long streamSize, double randomNumberOrigin, double randomNumberBound)
      Returns a stream producing the givenstreamSize number of pseudorandomdouble values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      IntStreamints()
      Returns an effectively unlimited stream of pseudorandomint values from this generator and/or one split from it.
      IntStreamints​(int randomNumberOrigin, int randomNumberBound)
      Returns an effectively unlimited stream of pseudorandom int values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      IntStreamints​(long streamSize)
      Returns a stream producing the givenstreamSize number of pseudorandomint values from this generator and/or one split from it.
      IntStreamints​(long streamSize, int randomNumberOrigin, int randomNumberBound)
      Returns a stream producing the givenstreamSize number of pseudorandomint values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      LongStreamlongs()
      Returns an effectively unlimited stream of pseudorandom long values from this generator and/or one split from it.
      LongStreamlongs​(long streamSize)
      Returns a stream producing the givenstreamSize number of pseudorandomlong values from this generator and/or one split from it.
      LongStreamlongs​(long randomNumberOrigin, long randomNumberBound)
      Returns an effectively unlimited stream of pseudorandom long values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      LongStreamlongs​(long streamSize, long randomNumberOrigin, long randomNumberBound)
      Returns a stream producing the givenstreamSize number of pseudorandomlong values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      booleannextBoolean()
      Returns a pseudorandomboolean value.
      voidnextBytes​(byte[] bytes)
      Fills a user-supplied byte array with generated pseudorandom bytes.
      doublenextDouble()
      Returns a pseudorandomdouble value between zero (inclusive) and one (exclusive).
      doublenextDouble​(double bound)
      Returns a pseudorandomdouble value between 0.0 (inclusive) and the specified bound (exclusive).
      doublenextDouble​(double origin, double bound)
      Returns a pseudorandomdouble value between the specified origin (inclusive) and bound (exclusive).
      intnextInt()
      Returns a pseudorandomint value.
      intnextInt​(int bound)
      Returns a pseudorandomint value between zero (inclusive) and the specified bound (exclusive).
      intnextInt​(int origin, int bound)
      Returns a pseudorandomint value between the specified origin (inclusive) and the specified bound (exclusive).
      longnextLong()
      Returns a pseudorandomlong value.
      longnextLong​(long bound)
      Returns a pseudorandomlong value between zero (inclusive) and the specified bound (exclusive).
      longnextLong​(long origin, long bound)
      Returns a pseudorandomlong value between the specified origin (inclusive) and the specified bound (exclusive).
      SplittableRandomsplit()
      Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance.

    • Constructor Detail

      • SplittableRandom

        public SplittableRandom​(long seed)
        Creates a new SplittableRandom instance using the specified initial seed. SplittableRandom instances created with the same seed in the same program generate identical sequences of values.
        Parameters:
        seed - the initial seed

      • SplittableRandom

        public SplittableRandom()
        Creates a new SplittableRandom instance that is likely to generate sequences of values that are statistically independent of those of any other instances in the current program; and may, and typically does, vary across program invocations.

    • Method Detail

      • split

        public SplittableRandom split()
        Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance. However, with very high probability, the set of values collectively generated by the two objects has the same statistical properties as if the same quantity of values were generated by a single thread using a single SplittableRandom object. Either or both of the two objects may be further split using thesplit() method, and the same expected statistical properties apply to the entire set of generators constructed by such recursive splitting.
        Returns:
        the new SplittableRandom instance

      • nextBytes

        public void nextBytes​(byte[] bytes)
        Fills a user-supplied byte array with generated pseudorandom bytes.
        Parameters:
        bytes - the byte array to fill with pseudorandom bytes
        Throws:
        NullPointerException - if bytes is null
        Since:
        10

      • nextInt

        public int nextInt()
        Returns a pseudorandomint value.
        Returns:
        a pseudorandomint value

      • nextInt

        public int nextInt​(int bound)
        Returns a pseudorandomint value between zero (inclusive) and the specified bound (exclusive).
        Parameters:
        bound - the upper bound (exclusive). Must be positive.
        Returns:
        a pseudorandomint value between zero (inclusive) and the bound (exclusive)
        Throws:
        IllegalArgumentException - ifbound is not positive

      • nextInt

        public int nextInt​(int origin,                   int bound)
        Returns a pseudorandomint value between the specified origin (inclusive) and the specified bound (exclusive).
        Parameters:
        origin - the least value returned
        bound - the upper bound (exclusive)
        Returns:
        a pseudorandomint value between the origin (inclusive) and the bound (exclusive)
        Throws:
        IllegalArgumentException - iforigin is greater than or equal tobound

      • nextLong

        public long nextLong()
        Returns a pseudorandomlong value.
        Returns:
        a pseudorandomlong value

      • nextLong

        public long nextLong​(long bound)
        Returns a pseudorandomlong value between zero (inclusive) and the specified bound (exclusive).
        Parameters:
        bound - the upper bound (exclusive). Must be positive.
        Returns:
        a pseudorandomlong value between zero (inclusive) and the bound (exclusive)
        Throws:
        IllegalArgumentException - ifbound is not positive

      • nextLong

        public long nextLong​(long origin,                     long bound)
        Returns a pseudorandomlong value between the specified origin (inclusive) and the specified bound (exclusive).
        Parameters:
        origin - the least value returned
        bound - the upper bound (exclusive)
        Returns:
        a pseudorandomlong value between the origin (inclusive) and the bound (exclusive)
        Throws:
        IllegalArgumentException - iforigin is greater than or equal tobound

      • nextDouble

        public double nextDouble()
        Returns a pseudorandomdouble value between zero (inclusive) and one (exclusive).
        Returns:
        a pseudorandomdouble value between zero (inclusive) and one (exclusive)

      • nextDouble

        public double nextDouble​(double bound)
        Returns a pseudorandomdouble value between 0.0 (inclusive) and the specified bound (exclusive).
        Parameters:
        bound - the upper bound (exclusive). Must be positive.
        Returns:
        a pseudorandomdouble value between zero (inclusive) and the bound (exclusive)
        Throws:
        IllegalArgumentException - ifbound is not positive

      • nextDouble

        public double nextDouble​(double origin,                         double bound)
        Returns a pseudorandomdouble value between the specified origin (inclusive) and bound (exclusive).
        Parameters:
        origin - the least value returned
        bound - the upper bound (exclusive)
        Returns:
        a pseudorandomdouble value between the origin (inclusive) and the bound (exclusive)
        Throws:
        IllegalArgumentException - iforigin is greater than or equal tobound

      • nextBoolean

        public boolean nextBoolean()
        Returns a pseudorandomboolean value.
        Returns:
        a pseudorandomboolean value

      • ints

        public IntStream ints​(long streamSize)
        Returns a stream producing the givenstreamSize number of pseudorandomint values from this generator and/or one split from it.
        Parameters:
        streamSize - the number of values to generate
        Returns:
        a stream of pseudorandomint values
        Throws:
        IllegalArgumentException - ifstreamSize is less than zero

      • ints

        public IntStream ints()
        Returns an effectively unlimited stream of pseudorandomint values from this generator and/or one split from it.
        Implementation Note:
        This method is implemented to be equivalent to ints(Long.MAX_VALUE).
        Returns:
        a stream of pseudorandomint values

      • ints

        public IntStream ints​(long streamSize,                      int randomNumberOrigin,                      int randomNumberBound)
        Returns a stream producing the givenstreamSize number of pseudorandomint values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
        Parameters:
        streamSize - the number of values to generate
        randomNumberOrigin - the origin (inclusive) of each random value
        randomNumberBound - the bound (exclusive) of each random value
        Returns:
        a stream of pseudorandomint values, each with the given origin (inclusive) and bound (exclusive)
        Throws:
        IllegalArgumentException - ifstreamSize is less than zero, orrandomNumberOrigin is greater than or equal torandomNumberBound

      • ints

        public IntStream ints​(int randomNumberOrigin,                      int randomNumberBound)
        Returns an effectively unlimited stream of pseudorandom int values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
        Implementation Note:
        This method is implemented to be equivalent to ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
        Parameters:
        randomNumberOrigin - the origin (inclusive) of each random value
        randomNumberBound - the bound (exclusive) of each random value
        Returns:
        a stream of pseudorandomint values, each with the given origin (inclusive) and bound (exclusive)
        Throws:
        IllegalArgumentException - ifrandomNumberOrigin is greater than or equal torandomNumberBound

      • longs

        public LongStream longs​(long streamSize)
        Returns a stream producing the givenstreamSize number of pseudorandomlong values from this generator and/or one split from it.
        Parameters:
        streamSize - the number of values to generate
        Returns:
        a stream of pseudorandomlong values
        Throws:
        IllegalArgumentException - ifstreamSize is less than zero

      • longs

        public LongStream longs()
        Returns an effectively unlimited stream of pseudorandom long values from this generator and/or one split from it.
        Implementation Note:
        This method is implemented to be equivalent to longs(Long.MAX_VALUE).
        Returns:
        a stream of pseudorandomlong values

      • longs

        public LongStream longs​(long streamSize,                        long randomNumberOrigin,                        long randomNumberBound)
        Returns a stream producing the givenstreamSize number of pseudorandomlong values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
        Parameters:
        streamSize - the number of values to generate
        randomNumberOrigin - the origin (inclusive) of each random value
        randomNumberBound - the bound (exclusive) of each random value
        Returns:
        a stream of pseudorandomlong values, each with the given origin (inclusive) and bound (exclusive)
        Throws:
        IllegalArgumentException - ifstreamSize is less than zero, orrandomNumberOrigin is greater than or equal torandomNumberBound

      • longs

        public LongStream longs​(long randomNumberOrigin,                        long randomNumberBound)
        Returns an effectively unlimited stream of pseudorandom long values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
        Implementation Note:
        This method is implemented to be equivalent to longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
        Parameters:
        randomNumberOrigin - the origin (inclusive) of each random value
        randomNumberBound - the bound (exclusive) of each random value
        Returns:
        a stream of pseudorandomlong values, each with the given origin (inclusive) and bound (exclusive)
        Throws:
        IllegalArgumentException - ifrandomNumberOrigin is greater than or equal torandomNumberBound

      • doubles

        public DoubleStream doubles​(long streamSize)
        Returns a stream producing the givenstreamSize number of pseudorandomdouble values from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).
        Parameters:
        streamSize - the number of values to generate
        Returns:
        a stream ofdouble values
        Throws:
        IllegalArgumentException - ifstreamSize is less than zero

      • doubles

        public DoubleStream doubles()
        Returns an effectively unlimited stream of pseudorandom double values from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).
        Implementation Note:
        This method is implemented to be equivalent to doubles(Long.MAX_VALUE).
        Returns:
        a stream of pseudorandomdouble values

      • doubles

        public DoubleStream doubles​(long streamSize,                            double randomNumberOrigin,                            double randomNumberBound)
        Returns a stream producing the givenstreamSize number of pseudorandomdouble values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
        Parameters:
        streamSize - the number of values to generate
        randomNumberOrigin - the origin (inclusive) of each random value
        randomNumberBound - the bound (exclusive) of each random value
        Returns:
        a stream of pseudorandomdouble values, each with the given origin (inclusive) and bound (exclusive)
        Throws:
        IllegalArgumentException - ifstreamSize is less than zero, orrandomNumberOrigin is greater than or equal torandomNumberBound

      • doubles

        public DoubleStream doubles​(double randomNumberOrigin,                            double randomNumberBound)
        Returns an effectively unlimited stream of pseudorandom double values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
        Implementation Note:
        This method is implemented to be equivalent to doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
        Parameters:
        randomNumberOrigin - the origin (inclusive) of each random value
        randomNumberBound - the bound (exclusive) of each random value
        Returns:
        a stream of pseudorandomdouble values, each with the given origin (inclusive) and bound (exclusive)
        Throws:
        IllegalArgumentException - ifrandomNumberOrigin is greater than or equal torandomNumberBound