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Thread: Random Numbers on button

1. Registered User
Join Date
Sep 2005
Posts
22

Random Numbers on button

Hi,

I was wondering how do i go about generating unique random numbers?
ie
i want to generate numbers between 0-9 randomly. I dont want to repeat the numbers.Then that no: should display on the buttons.ie there are 9 buttons. first randomly generated number should display on the first button & 2nd no: should display on 2nd button. & so on for example I have the numbers 9371482065 then 9 should display on the first button ,3 should display on 2nd button ....
But the following code i'm having is repeating some numbers...can any one help me in solving...please.....

code::::

Random rgen = new Random(); // Random number generator
int[] cards = new int[10];

// --- Initialize the array to the ints 0-51
for (int i=0; i<10; i++) {
cards[i] = i;
}

// --- Shuffle by exchanging each element randomly
for (int i=0; i<10; i++) {
int randomPosition = rgen.nextInt(10);
System.out.println(" randomPosition " + randomPosition);
int temp = cards[i];
System.out.println(" temp" + temp);
cards[i] = cards[randomPosition];
cards[randomPosition] = temp;

System.out.println(" Random Number" + cards[randomPosition]);

}

2. Registered User
Join Date
Oct 2004
Location
Chicago
Posts
108
Computers can't generate real random numbers but you can get some real random numbers here http://www.fourmilab.ch/hotbits/

3. I think this is random enough for your purpose

The idea is to stuff the random numbers into a HashSet as you go along.
When the size of the hashset is 10 you know that it contains 10
unique integers.

Code:
import java.util.*;

public class Ramdomizer {
public static Random rand=new Random(System.currentTimeMillis());
static HashSet hs=new HashSet();

public Ramdomizer() {}

public int [] getRandoms(int maxNo) {
hs.clear();
while (true) {
int n = rand.nextInt(maxNo);
hs.add(new Integer(n));
if (hs.size() == maxNo) {
break;
}
}
int [] ret=new int[maxNo];
Iterator it=hs.iterator();
int cnt=0;
while (it.hasNext()) {
ret[cnt++]=((Integer)it.next()).intValue();
}
return shuffle(ret);
}

private int [] shuffle(int [] arr) {
for (int i=0; i<arr.length; i++) {
int rp = rand.nextInt(10);
int tmp=arr[rp];
arr[rp]=arr[i];
arr[i]=tmp;
}
return arr;
}
/**
* *********** MAIN ***********
*/
public static void main(String[] args) {
Ramdomizer rd = new Ramdomizer();
int [] rn=rd.getRandoms(10);
showResult(rn);
rn=rd.getRandoms(10);
showResult(rn);
}
private static void showResult(int[] rn) {
for (int i=0; i<rn.length; i++) {
System.out.println(i+": "+rn[i]);
}
}
}
Last edited by sjalle; 10-07-2005 at 09:46 AM.

4. Registered User
Join Date
Oct 2005
Posts
40
Originally Posted by daina
Hi,

I was wondering how do i go about generating unique random numbers?
ie
i want to generate numbers between 0-9 randomly. I dont want to repeat the numbers.Then that no: should display on the buttons.ie there are 9 buttons. first randomly generated number should display on the first button & 2nd no: should display on 2nd button. & so on for example I have the numbers 9371482065 then 9 should display on the first button ,3 should display on 2nd button ....
But the following code i'm having is repeating some numbers...can any one help me in solving...please.....

code::::

Random rgen = new Random(); // Random number generator
int[] cards = new int[10];

// --- Initialize the array to the ints 0-51
for (int i=0; i<10; i++) {
cards[i] = i;
}

// --- Shuffle by exchanging each element randomly
for (int i=0; i<10; i++) {
int randomPosition = rgen.nextInt(10);
System.out.println(" randomPosition " + randomPosition);
int temp = cards[i];
System.out.println(" temp" + temp);
cards[i] = cards[randomPosition];
cards[randomPosition] = temp;

System.out.println(" Random Number" + cards[randomPosition]);

}

Read your code again. Its perfect! You just need to print the cards array in another loop after the first for loop and you will get desired result.

Regards,
Mohit

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