randomNumbers
Class RandomDist

java.lang.Object
  randomNumbers.RandomDist

public class RandomDist

extends java.lang.Object

Demonstrates the difference in Random number distrobution using
Math.random() * n, Random.nextInt() % n and Random.nextInt(int n)

Given a randon number between a given range (0 to n) then if the distrobution was random then we should be able to expect that roughly half the numbers generated are in the range 0 to ((n/2)-1) whilst the rest are in the range n/2 to n-1.

However, the results of this program are:

Random number range is 0 to 1431655764
Using Math.random * n the number below 715827882 is 500714
Using Random.nextInt() % n the number below 715827882 is 666540
Using Random.nextInt(n) the number below 715827882 is 501091


This demonstrates a problem with using Random.nextInt() % n as there are significantly more values below the halfway point than there should be!

Top Tip: always use Random.nextInt(n)

Field Summary

private static java.util.Random

rnd

Constructor Summary

RandomDist()

Method Summary

static void

main(java.lang.String[] args) main method - This is simply a functional program.

Methods inherited from class java.lang.Object

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

Field Detail

rnd

private static java.util.Random rnd

Constructor Detail

RandomDist

public RandomDist()

Method Detail

main

public static void main(java.lang.String[] args)

main method - This is simply a functional program.