Which data structure to use?

Hello,

I need a data structure which:

1) I will be able to remove an item (without knowing the index of that item)
2) I can draw an item randomly (normally in an array, I generate a random number and draw that item in that index.. data structures that use keys -hashtables, hashmaps vs need an iterator to go through the items)
3) I will be able to add an item (the adding order does not matter)

Which data structure gives faster solutions?

Thanks..

HashSet can do all of those things. For #2, you have to use the toArray() method, though.

Good idea. Have you got any idea about the performance of converting a HashSet to an array?

Thanks for the reply.

I'm sorry, I don't know the answer to that. I'm guessing it would be O(N), since you have to move the elements one by one. But I'm not sure.

Yes, it should depend on the size of the HashSet, I guess.
Thanks again.