How can I store a list of parse objects from one column into a HashSet?

Question

If I have a String column "A" in a parse class. And I have 5 objects in column "A" with values:

1- A'
2- B'
3- C'
4- D'
5- E'

How can I retrieve those objects, and store them in HashSet to be used? So, if I system.out.println the HashSet values, it would show me A',B',C',D',E'. Note: I am trying to add a list of parse objects into a hashSet. So I retrieve a whole column, like I said above, and store it into a hashSet.

Need more information? Ask instead of -1ing please.