The figure below shows the structure of Singly LinkedList. Consider the following java codes that implements Singly LinkedList. public class Node\{ private Object element; private Node next; ... // the constructor, methods setElement(), setNext(), getElement(), getNext() are omitted 3 public class SLL \{ private Node head; ... // the constructor, methods setHead(), getHead(), add(), remove() are omitted \} Write a method in class SLL to find the middle element. Specifically, 1. The method returns null if the Singly LinkedList is empty; 2. The method returns the 2n+1 th node if the Singly LinkedList has n nodes, where n is an odd number; 3. The method returns the 2n th node if the Singly LinkedList has n nodes, where n is an even number