import java.util.NoSuchElementException;

public class LinkedList<E extends Comparable<E>> {

    private static class Node<T> {
        private T value;
        private Node<T> next;

        private Node(T value, Node<T> next) {
            this.value = value;
            this.next = next;
        }
    }

    private Node<E> head = null;
    private int size;

    public void addFirst(E element) {

        if (element == null) {
            throw new NullPointerException();
        }

        head = new Node<E>(element, head);
        size++;
    }

    public int size() {
        return size(head);
    }
    
    private int size(Node<E> current) {
        
        int count = 0;
            
        if (current != null) {
            count = 1 + size(current.next);
        }

        return count;
    }


    public String toString() {
        String str = "[";
        Node<E> current = head;
        while (current != null) {
            if (current != head) {
                str += ",";
            }
            str += current.value;
            current = current.next;
        }
        str += "]";
        return str;
    }
    
    public static void main(String[] args) {

        LinkedList<Integer> xs = new LinkedList<Integer>();

        for (int i=4; i>=0; i--) {
            xs.addFirst(i);
        }

        System.out.println(xs);
        System.out.println(xs.size());
        
    }
}