Inner class and interface question (I posted some really long code)

I'm want to put the getHead() method in the BagInterface. However, I
can't do this because the compiler keeps saying it can't find 'class
Node' in Location BagInterface<T>. I guess this is because Node is an
inner class of my LinkedList class. Ideas how to fix this? Ideally I
want to preserve the inner class. Below is the complete working code
in question.

public class Main {

    public static void main(String[] args) {
        BagInterface <Integer> list = new LinkedList <Integer>();
        list.add(new Integer(1));
        list.add(new Integer(2));
        list.add(new Integer(100));
        list.add(new Integer(100));
        list.add(new Integer(100));
        list.add(new Integer(100));
        list.add(new Integer(99));
        list.add(new Integer(11));
        list.printMe();
        //System.out.println("The sum is " +
list.sumMe(list.getHead()));

    }//end main
}

interface BagInterface<T> {
    public void add(T newData);
    public void printMe();
    public Node getHead(); //<---Problem Line

}

class LinkedList<T> implements BagInterface<T>{

    private Node firstNode;
    private int numberOfEntries;

    public LinkedList() {
        firstNode = null;
        numberOfEntries = 0;
    }

    class Node {

        private T data;
        Node next;

        Node(T newData) {
            this(newData, null);
        }

        Node(T newData, Node nextNode) {
            data = newData;
            next = nextNode;
        }

        Node getHead() {
            return firstNode;
        }
    }//end class Node

    public Node getNext() {
        return firstNode.next;
    }

    public Node getHead() {
        return firstNode;
    }

    public void add(T newData) {
        Node newNode = new Node(newData);
        newNode.next = firstNode;
        firstNode = newNode;
        numberOfEntries++;
    }//end add

    public void printMe() {
        Node current = firstNode;

        while (current != null) {
            System.out.println(current.data);
            current = current.next;
        }
    }

}