How to make arraylist only access original values not duplicates

Question

To Make arraylist like as. HashSet?? code is needed

Answer 1

The easiest way to remove repeated elements is to add the contents to a Set (which will not allow duplicates) and then add the Set back to the ArrayList:

List<String> al = new ArrayList<>();
Set<String> hs = new HashSet<>();
hs.addAll(al);
al.clear();
al.addAll(hs);