List to TreeSet conversion produces: “java.lang.ClassCastException: MyClass cannot be cast to java.lang.Comparable”

Question

List myclassList = (List) rs.get();

TreeSet myclassSet = new TreeSet(myclassList);

I d

Answer 1

If you just want the set to remove duplicates, used a HashSet, although that will shuffle the order of the objects returned by the Iterator in ways that appear random.
But if you want to preserve the order somewhat, use LinkedHashSet, that will at least preserve the insertion order of the list.

TreeSet is only appropriate if you need the Set sorted, either by the Object's implementation of Comparable or by a custom Comparator passed to the TreeSet's constructor.