Question

For my specific purposes, I need to generate a whole number between 1 and 120 inclusive (which I can do no problem).

Once that number has been generated, I need to pull it from the pool so it can’t be generated again.

Continue this process until all numbers are exhausted, at which point, the pool fills back up and we start over again.

How could I go about doing this?

Answer 1

Generate the whole list of numbers from 1 to 120. Shuffle the list. Take the first element (and remove it)

List<Integer> list = new LinkedList<Integer>();
for (int i = 1; i <= 120; i++) {
    list.add(i)
}
Collections.shuffle(list);
...
int random = list.remove(0);
...
int otherRandom = list.remove(0);

Check for list.empty() in case you run out of numbers. If empty, create the list again and shuffle it.