Is there an easy way to select Items randomly from a data structure?

Question

Put simply, I want to implement a "bag" data structure. So, when i select an item I don't know which one i'm going to get. I want to be able to select all the items once (so no replacing of items i.e. selecting the same item twice in one session).
I can think of ways to implement it using random number generators and the like but does anyone know of a simple datastructure that will encapsulate this "bag" functionality and make my life simple. Hash tables maybe? Any pointers appreciated.
Chris.

Answer 1

I don't think there is anything like this in the collections framework but writing one as an extension of a vector could be simple. Something like:
public class Bag extends Vector {
  private Random _random = new Random();
  public Object pickRandom() {
    return this.remove(this._random.nextInt(this.size()));
}To add objects to the bag you just use the add(Object o) method (specified by the List interface, implemented by Vector). To "grab" one just call pickRandom().