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5 Replies Latest reply: Jul 26, 2013 12:08 AM by e697c280-00bc-47ab-a0c8-c131b4db31be RSS

How to generate 10 DIFFERENT random numbers?

843785 Newbie
Currently Being Moderated
I'm trying to fill an ArrayList with ten different random numbers (out of 20 numbers). I just can't seem to get it right. I've tried many things and I think I'm drifting farther away from the solution as I go on.

Two requests:

1) An efficient way to do this.
2) Point out what goes wrong with my incorrect approach so I learn something.


The last approach I came up with looks like this. But the loop never ends...

import java.util.ArrayList;
import java.util.Random;

public class RandomDifferent {
public static void main(String args[]) {

Random randomNumber = new Random();
int random;

ArrayList<Integer> b = new ArrayList<Integer>();

while (b.size() < 10) {
for (int y=0; y<10; y++) {
random = randomNumber.nextInt(20);
for (int i = 0; i<b.size(); i++) {
if (b.get(i) != random)

for (int y=0; y<b.size(); y++) {