add abstract method

void add(T element)

Adds the specified element element into the underlying collection immediately before the element that would be returned by next, if any, and after the element that would be returned by previous, if any. (If the collection contains no elements, the new element becomes the sole element in the collection.) The new element is inserted before the implicit cursor: a subsequent call to next would be unaffected, and a subsequent call to previous would return the new element. (This call increases by one the value
that would be returned by a call to nextIndex or previousIndex.)

Implementation

void add(T element);