Scala example source code file (Random.scala)

This example Scala source code file (Random.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

a, canbuildfrom, cc, cc, char, double, float, int, int, long, long, random, random, stream

The Scala Random.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2006-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.util

import collection.mutable.ArrayBuffer
import collection.generic.CanBuildFrom
import scala.collection.immutable.{ List, Stream }

/**
 *  @author Stephane Micheloud
 *
 */
class Random(val self: java.util.Random) {
  /** Creates a new random number generator using a single long seed. */
  def this(seed: Long) = this(new java.util.Random(seed))

  /** Creates a new random number generator using a single integer seed. */
  def this(seed: Int) = this(seed.toLong)

  /** Creates a new random number generator. */
  def this() = this(new java.util.Random())

  /** Returns the next pseudorandom, uniformly distributed boolean value
   *  from this random number generator's sequence.
   */
  def nextBoolean(): Boolean = self.nextBoolean()

  /** Generates random bytes and places them into a user-supplied byte
   *  array.
   */
  def nextBytes(bytes: Array[Byte]) { self.nextBytes(bytes) }

  /** Returns the next pseudorandom, uniformly distributed double value
   *  between 0.0 and 1.0 from this random number generator's sequence.
   */
  def nextDouble(): Double = self.nextDouble()

  /** Returns the next pseudorandom, uniformly distributed float value
   *  between 0.0 and 1.0 from this random number generator's sequence.
   */
  def nextFloat(): Float = self.nextFloat()

  /** Returns the next pseudorandom, Gaussian ("normally") distributed
   *  double value with mean 0.0 and standard deviation 1.0 from this
   *  random number generator's sequence.
   */
  def nextGaussian(): Double = self.nextGaussian()

  /** Returns the next pseudorandom, uniformly distributed int value
   *  from this random number generator's sequence.
   */
  def nextInt(): Int = self.nextInt()

  /** Returns a pseudorandom, uniformly distributed int value between 0
   *  (inclusive) and the specified value (exclusive), drawn from this
   *  random number generator's sequence.
   */
  def nextInt(n: Int): Int = self.nextInt(n)

  /** Returns the next pseudorandom, uniformly distributed long value
   *  from this random number generator's sequence.
   */
  def nextLong(): Long = self.nextLong()
  
  /** Returns a pseudorandomly generated String.  This routine does
   *  not take any measures to preserve the randomness of the distribution
   *  in the face of factors like unicode's variable-length encoding,
   *  so please don't use this for anything important.  It's primarily
   *  intended for generating test data.
   *
   *  @param  length    the desired length of the String
   *  @return           the String
   */
  def nextString(length: Int) = {
    def safeChar() = {
      val surrogateStart: Int = 0xD800
      val res = nextInt(surrogateStart - 1) + 1
      res.toChar
    }
    
    List.fill(length)(safeChar()).mkString
  }
  
  /** Returns the next pseudorandom, uniformly distributed value
   *  from the ASCII range 33-126.
   */
  def nextPrintableChar(): Char = {
    val low  = 33
    val high = 127
    (self.nextInt(high - low) + low).toChar
  }

  def setSeed(seed: Long) { self.setSeed(seed) }
    
  /** Returns a new collection of the same type in a randomly chosen order.
   * 
   *  @param  coll    the TraversableOnce to shuffle
   *  @return         the shuffled TraversableOnce
   */
  def shuffle[T, CC[X] <: TraversableOnce[X]](xs: CC[T])(implicit bf: CanBuildFrom[CC[T], T, CC[T]]): CC[T] = {
    val buf = new ArrayBuffer[T] ++= xs
        
    def swap(i1: Int, i2: Int) {
      val tmp = buf(i1)
      buf(i1) = buf(i2)
      buf(i2) = tmp
    }
    
    for (n <- buf.length to 2 by -1) {
      val k = nextInt(n)
      swap(n - 1, k)
    }
    
    bf(xs) ++= buf result
  }

}

/** The object <code>Random offers a default implementation
 *  of scala.util.Random and random-related convenience methods.
 *
 *  @since 2.8
 */
object Random extends Random {
  
  /** Returns a Stream of pseudorandomly chosen alphanumeric characters,
   *  equally chosen from A-Z, a-z, and 0-9.
   * 
   *  @since 2.8
   */
  def alphanumeric: Stream[Char] = {
    def isAlphaNum(c: Char) = (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9')

    Stream continually nextPrintableChar filter isAlphaNum
  }

}