COWBELL CYBER, Inc. interview question

Those for question: No introduction, Open notepad 1. write immutable class - I written it correctly - class had one another class reference field - iv asked question about it saying do we need to make this referred class as final as well ? I ans not required (This ans is partially correct - for perfect immutable class it is needed to be final and for only immutable class not needed) 2. Shallow and deep copy - ans correctly 3. Use stream api and sort the objects on the basis of some class field like id or name -- partially answered not able to collect the syntacx for comparator in stream func. Prepare these questions may be same will be asked by Iv and you will get selected