Java random without repetition

Question

How can I implement an integer random, that can generate each number just one time but without repetition. I use this code in Android.

int random = Random.nextInt((max+1 - min) + min;

Problem: between max and min there is repeated numbers and also some numbers, they don't exist.

What do you need this for? In any case, you don't want to use `Random`, you should see [this post](https://stackoverflow.com/questions/5505927/how-to-generate-a-random-permutation-in-java) — F. Stephen Q, Sep 04 '15 at 04:37

score 3 · Accepted Answer · answered Sep 04 '15 at 04:38

3

You need a shuffle algorithm

create an array/list of the possible number, shuffle it, and then get the number once at a time

answered Sep 04 '15 at 04:38

Derek Fung

score 0 · Answer 2 · answered Sep 04 '15 at 04:41

0

instead of having a list (as mentioned from Derek Fung) with all possible values you

can store created values in an list
check if any new created value is in that list and then
- add it to the list
- or create a new value until you found one that is not in the list

answered Sep 04 '15 at 04:41

Martin Frank

Set would be better for that, wouldn't it? – piezol Sep 04 '15 at 07:17
@piezol depends on implementation, if it's a simple `java.util.List` it might be enough to simply add these... – Martin Frank Sep 04 '15 at 07:38

2 Answers2