From java docs:
public boolean add(E e)
Appends the specified element to the end of this list.
This method is equivalent to addLast(E).
Specified by:
add in interface Collection<E>
Specified by:
add in interface Deque<E>
Specified by:
add in interface List<E>
Specified by:
add in interface Queue<E>
Overrides:
add in class AbstractList<E>
Parameters:
e - element to be appended to this list
Returns:
true (as specified by Collection.add(E))
In your case the you add 'B' for the end of the list after you added 'F' to the end of the list