Create Subsets2

Given a collection of integers that might contain duplicates, S, return all possible subsets.

Note:

Elements in a subset must be in non-descending order.
The solution set must not contain duplicate subsets.
For example,
If S = [1,2,2], a solution is:

[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]
(java ArrayList 有个方法叫做contains()可以判断有没有某个元素了，然后结合上面那个Collections.sort(ArrayList))