Assured 6 digit random number

问题:

I have to Generate a 6 digit Random Number. The below is the Code that I have done so far. It works fine but some time its giving 7 digits in place of 6 digits.

The main question is why?

How do I generate an assured 6 digit random number?

val ran = new Random()
val code= (100000 + ran.nextInt(999999)).toString

回答1:

If ran.nextInt() returns a number larger than 900000, then the sum will be a 7 digit number.

The fix is to make sure this does not happen. Since Random.nextInt(n) returns a number that is less than n, the following will work.

val code= (100000 + ran.nextInt(900000)).toString()

回答2:

It's because nextInt() Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive)

You have to decrease your right border on one.

回答3:

val code= (100000 + ran.nextInt(999999)).toString

The problem is ran.nextInt(999999) might return number greater than 899999, which would result in 7-digit-number together if you add 100000.

Try change it to

val code= (100000 + ran.nextInt(899999)).toString

This will ensure your random number to be more than or equal to 100000 and less than or equal to 999999.

回答4:

Another approach, for

import scala.util.Random
val rand = new Random()

consider a vector of 6 random digits,

val randVect = (1 to 6).map { x => rand.nextInt(10) }

Then, cast the vector onto an integral value,

randVect.mkString.toLong

This proceeding is general enough to cope with any number of digits. If Long cannot represent the vector, consider BigInt.

Update

Moreover, wrap it into an implicit class, noting that the first digit ought not be zero,

implicit class RichRandom(val rand: Random) extends AnyVal {
  def fixedLength(n: Int) = {
    val first = rand.nextInt(9)+1
    val randVect = first +: (1 until n).map { x => rand.nextInt(10) }
    BigInt(randVect.mkString)
  }
}

so it can be used as

scala> rand.fixedLength(6)
res: scala.math.BigInt = 689305

scala> rand.fixedLength(15)
res: scala.math.BigInt = 517860820348342

回答5:

If you want a random number which can start with zeros, consider this:

import scala.util.Random
val r = new Random()
(1 to 6).map { _ => r.nextInt(10).toString }.mkString

回答6:

Starting Scala 2.13, scala.util.Random provides:

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

which used as follow, generates a 6-digit Int (between 100_000 (included) and 1_000_000 (excluded)):

import scala.util.Random
Random.between(100000, 1000000) // in [100000, 1000000[

回答7:

import scala.util.Random
math.ceil(Random.nextFloat()*1E6).toInt

回答8:

    min=100000
    max=999999
    ans=rand()%(max-min)+min