Generating random unique sequences in Java

Question

I have an array of numbers, let's say for example it's

[1, 3, 5, 7, 9]

It is possible to generate 5! that is 120 unique sequences of these numbers. For example

1 3 5 7 9
5 1 3 9 7
7 3 9 5 1
1 7 9 5 3
... and so forth

I need to generate 10 of these sequences randomly, with no duplicates. Any suggestions would be much appreciated.

Answer 1

List<Integer> template = Arrays.asList(1, 3, 5, 7, 9);
Set<List<Integer>> seen = new HashSet<List<Integer>>();
for (int i = 0; i < 10; ++i) {
    List<Integer> items = new ArrayList<Integer>(template);
    do {
        Collections.shuffle(items);
    } while (!seen.add(items));
    System.out.println(items);
}

:-)