Package org.apache.commons.lang3

Class RandomUtils

  • public class RandomUtils
extends java.lang.Object
    Supplements the standard Random class.

    Use secure() to get the singleton instance based on SecureRandom.getInstanceStrong() which uses an algorithms/providers specified in the securerandom.strongAlgorithms Security property.

    Use insecure() to get the singleton instance based on ThreadLocalRandom.current(); which is not cryptographically secure.

    Starting in version 3.15.0, this class uses SecureRandom.getInstanceStrong() for static methods.

    Starting in version 3.16.0, this class uses secure() for static methods and adds insecure().

    Before version 3.15.0, this class used ThreadLocalRandom.current() for static methods, which is 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).

    Since:
    3.3
    See Also:
    RandomStringUtils

    • Constructor Summary

      Constructors 
      Constructor Description
      RandomUtils()
      Deprecated.
      TODO Make private in 4.0.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static boolean nextBoolean()
      Generates a random boolean value.
      static byte[] nextBytes​(int count)
      Generates an array of random bytes.
      static double nextDouble()
      Generates a random double between 0 (inclusive) and Double.MAX_VALUE (exclusive).
      static double nextDouble​(double startInclusive, double endExclusive)
      Generates a random double within the specified range.
      static float nextFloat()
      Generates a random float between 0 (inclusive) and Float.MAX_VALUE (exclusive).
      static float nextFloat​(float startInclusive, float endExclusive)
      Generates a random float within the specified range.
      static int nextInt()
      Generates a random int between 0 (inclusive) and Integer.MAX_VALUE (exclusive).
      static int nextInt​(int startInclusive, int endExclusive)
      Generates a random integer within the specified range.
      static long nextLong()
      Generates a random long between 0 (inclusive) and Long.MAX_VALUE (exclusive).
      static long nextLong​(long startInclusive, long endExclusive)
      Generates a random long within the specified range.
      boolean randomBoolean()
      Generates a random boolean value.
      byte[] randomBytes​(int count)
      Generates an array of random bytes.
      double randomDouble()
      Generates a random double between 0 (inclusive) and Double.MAX_VALUE (exclusive).
      double randomDouble​(double startInclusive, double endExclusive)
      Generates a random double within the specified range.
      float randomFloat()
      Generates a random float between 0 (inclusive) and Float.MAX_VALUE (exclusive).
      float randomFloat​(float startInclusive, float endExclusive)
      Generates a random float within the specified range.
      int randomInt()
      Generates a random int between 0 (inclusive) and Integer.MAX_VALUE (exclusive).
      int randomInt​(int startInclusive, int endExclusive)
      Generates a random integer within the specified range.
      long randomLong()
      Generates a random long between 0 (inclusive) and Long.MAX_VALUE (exclusive).
      long randomLong​(long startInclusive, long endExclusive)
      Generates a random long within the specified range.
      static RandomUtils secure()
      Gets the singleton instance based on SecureRandom.getInstanceStrong() which uses an algorithms/providers specified in the securerandom.strongAlgorithms Security property.
      java.lang.String toString()  

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • RandomUtils

        @Deprecated
public RandomUtils()
        Deprecated.
        TODO Make private in 4.0.
        RandomUtils instances should NOT be constructed in standard programming. Instead, the class should be used as RandomUtils.nextBytes(5);.

        This constructor is public to permit tools that require a JavaBean instance to operate.

    • Method Detail

      • nextBoolean

        public static boolean nextBoolean()
        Generates a random boolean value.
        Returns:
        the random boolean
        Since:
        3.5

      • nextBytes

        public static byte[] nextBytes​(int count)
        Generates an array of random bytes.
        Parameters:
        count - the size of the returned array
        Returns:
        the random byte array
        Throws:
        java.lang.IllegalArgumentException - if count is negative

      • nextDouble

        public static double nextDouble()
        Generates a random double between 0 (inclusive) and Double.MAX_VALUE (exclusive).
        Returns:
        the random double
        Since:
        3.5
        See Also:
        nextDouble(double, double)

      • nextDouble

        public static double nextDouble​(double startInclusive,
                                double endExclusive)
        Generates a random double within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random double
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative

      • nextFloat

        public static float nextFloat()
        Generates a random float between 0 (inclusive) and Float.MAX_VALUE (exclusive).
        Returns:
        the random float
        Since:
        3.5
        See Also:
        nextFloat(float, float)

      • nextFloat

        public static float nextFloat​(float startInclusive,
                              float endExclusive)
        Generates a random float within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random float
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative

      • nextInt

        public static int nextInt()
        Generates a random int between 0 (inclusive) and Integer.MAX_VALUE (exclusive).
        Returns:
        the random integer
        Since:
        3.5
        See Also:
        nextInt(int, int)

      • nextInt

        public static int nextInt​(int startInclusive,
                          int endExclusive)
        Generates a random integer within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random integer
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative

      • nextLong

        public static long nextLong()
        Generates a random long between 0 (inclusive) and Long.MAX_VALUE (exclusive).
        Returns:
        the random long
        Since:
        3.5
        See Also:
        nextLong(long, long)

      • nextLong

        public static long nextLong​(long startInclusive,
                            long endExclusive)
        Generates a random long within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random long
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative

      • secure

        public static RandomUtils secure()
        Gets the singleton instance based on SecureRandom.getInstanceStrong() which uses an algorithms/providers specified in the securerandom.strongAlgorithms Security property.

        The method SecureRandom.getInstanceStrong() is called on-demand.

        Returns:
        the singleton instance based on SecureRandom.getInstanceStrong().
        Since:
        3.16.0
        See Also:
        SecureRandom.getInstanceStrong()

      • randomBoolean

        public boolean randomBoolean()
        Generates a random boolean value.
        Returns:
        the random boolean
        Since:
        3.16.0

      • randomBytes

        public byte[] randomBytes​(int count)
        Generates an array of random bytes.
        Parameters:
        count - the size of the returned array
        Returns:
        the random byte array
        Throws:
        java.lang.IllegalArgumentException - if count is negative
        Since:
        3.16.0

      • randomDouble

        public double randomDouble()
        Generates a random double between 0 (inclusive) and Double.MAX_VALUE (exclusive).
        Returns:
        the random double
        Since:
        3.16.0
        See Also:
        nextDouble(double, double)

      • randomDouble

        public double randomDouble​(double startInclusive,
                           double endExclusive)
        Generates a random double within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random double
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative
        Since:
        3.16.0

      • randomFloat

        public float randomFloat()
        Generates a random float between 0 (inclusive) and Float.MAX_VALUE (exclusive).
        Returns:
        the random float
        Since:
        3.16.0
        See Also:
        nextFloat(float, float)

      • randomFloat

        public float randomFloat​(float startInclusive,
                         float endExclusive)
        Generates a random float within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random float
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative

      • randomInt

        public int randomInt()
        Generates a random int between 0 (inclusive) and Integer.MAX_VALUE (exclusive).
        Returns:
        the random integer
        Since:
        3.16.0
        See Also:
        nextInt(int, int)

      • randomInt

        public int randomInt​(int startInclusive,
                     int endExclusive)
        Generates a random integer within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random integer
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative
        Since:
        3.16.0

      • randomLong

        public long randomLong()
        Generates a random long between 0 (inclusive) and Long.MAX_VALUE (exclusive).
        Returns:
        the random long
        Since:
        3.16.0
        See Also:
        nextLong(long, long)

      • randomLong

        public long randomLong​(long startInclusive,
                       long endExclusive)
        Generates a random long within the specified range.
        Parameters:
        startInclusive - the smallest value that can be returned, must be non-negative
        endExclusive - the upper bound (not included)
        Returns:
        the random long
        Throws:
        java.lang.IllegalArgumentException - if startInclusive > endExclusive or if startInclusive is negative
        Since:
        3.16.0

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object