Scala Cookbook

2.7. Generating Random Numbers

Problem

You need to create random numbers, such as when testing an application, performing a simulation, and many other situations.

Solution

Create random numbers with the Scala scala.util.Random class. You can create random integers:

scala> val r = scala.util.Random
r: scala.util.Random = scala.util.Random@13eb41e5

scala> r.nextInt
res0: Int = −1323477914

You can limit the random numbers to a maximum value:

scala> r.nextInt(100)
res1: Int = 58

In this use, the Int returned is between 0 (inclusive) and the value you specify (exclusive), so specifying 100 returns an Int from 0 to 99.

You can also create random Float values:

// returns a value between 0.0 and 1.0
scala> r.nextFloat
res2: Float = 0.50317204

You can create random Double values:

// returns a value between 0.0 and 1.0
scala> r.nextDouble
res3: Double = 0.6946000981900997

You can set the seed value using an Int or Long when creating the Random object:

scala> val r = new scala.util.Random(100)
r: scala.util.Random = scala.util.Random@bbf4061

You can also set the seed value after a Random object has been created:

r.setSeed(1000L)

Discussion

The Random class handles all the usual use cases, including creating numbers, setting the maximum value of a random number range, and setting a seed value. You can also generate random characters:

// random characters
scala> r.nextPrintableChar
res0: Char = H

scala> r.nextPrintableChar
res1: Char = r

Scala makes it easy to create a random-length range of numbers, which is ...