In collection..when we want to add any string or value.. we use add function...actual function is public boolean add(Object elem

Answer 1

For example?
Java documentation doesn't declare like that the add function of collection

boolean add(E e)
Appends the specified element to the end of this list

Depending of the implementation (ArrayList, linked, so on) some validate duplicity, of null, but in all you can add directly the string