Get random number between two numbers in Scala

Question

How do I get a random number between two numbers say 20 to 30?

I tried:

val r = new scala.util.Random
r.nextInt(30)

This allows only upper bound value, but values always starts with 0. Is there a way to set lower bound value (to 20 in the example)?

Thanks!

Solution 1

You can use below. Both start and end will be inclusive.

val start = 20
val end   = 30
val rnd = new scala.util.Random
start + rnd.nextInt( (end - start) + 1 )  

In your case

val r = new scala.util.Random
val r1 = 20 + r.nextInt(( 30 - 20) + 1)

Solution 2

Starting Scala 2.13, scala.util.Random provides:

def between(minInclusive: Int, maxExclusive: Int): Int

which used as follow, generates an Int between 20 (included) and 30 (excluded):

import scala.util.Random
Random.between(20, 30) // in [20, 30[

Solution 3

Sure. Just do

20 + r. nextInt(10)

Solution 4

You can use java.util.concurrent.ThreadLocalRandom as an option. It's preferable in multithreaded environments.

val random: ThreadLocalRandom = ThreadLocalRandom.current()
val r = random.nextLong(20, 30 + 1) // returns value between 20 and 30 inclusively

Solution 5

Also scaling math.random value which ranges between 0 and 1 to the interval of interest, and converting the Double in this case to Int, e.g.

(math.random * (30-20) + 20).toInt

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