Randomnumber without duplicate

[Petranilla]

How do you generate random numbers in Java without duplicate? Thanks.

[IIM]

This question is already asked.Check this

There are many ways to generate unique random numbers.I am discussing two of them below:-

• Write the numbers sequentially in a list structure.
  Shuffle it.
  Take the first 'n'.
  This uses only a single Random instance.
• Another option

Call Random rand = new Random();rand.nextInt(78)
and store value in Set.If added successfully(means unique as set doesnot support duplicacy) means it is unique.
Check the size,if it is less than 3 then keep on adding.

[bguild]

Also, if you want to generate a large amount of random numbers (so that duplicates would happen often) and you don't have a list of elements to choose from, or don't want to copy your list so you can shuffle it, then you can also choose n without duplicates from a set of m by iterating like this:

java.util.Random r = new java.util.Random();
for(int i = 0; i < m; i++) {
    if(r.nextInt(m - i) < n) {
        choose i;
        n--;
    }
}

[jalpesh_007]

i think you should have to look at this
this
or
Here

your idea will be cleared.

Thanks

[jwenting]

And do realise that as soon as you filter the numbers to (for example) not have duplicates they're no longer random.