public class SimpleList<E> {
    private ListNode<E> list;
    /**
      Constructs an empty list.
     */
    public SimpleList(){
        list = null;
    }
    /**
      Constructs a single-item list containing x.
     */
    public SimpleList(E x) {
        list = new ListNode<E>(x,null);
    }
    /**
      Constructs a list with head x and tail l.
    */
    public SimpleList(E x, SimpleList<E> l) {
        list = new ListNode<E>(x, copyNodes(l.list));
    }
    /**
      Constructs a list containing node n. Used to create a
      SimpleList from a list of ListNodes.
     */
    public SimpleList(ListNode<E> n) {
        list = copyNodes(n);
    }
    /**
      Used to extract the head of a list.
      @throws Exceptions.ItemNotFound if the list is empty
      @return the head of the list
    */
    public E head() throws ItemNotFound { 
        if (isEmpty())
            throw new ItemNotFound("empty list");
        return list.element;
    }
    /**
      Used to extract the tail of a list. 
      @throws Exceptions.ItemNotFound if the list is empty.
      @return the tail of the list
    */
    public SimpleList<E> tail() throws ItemNotFound {
        if (isEmpty())
            throw new ItemNotFound("empty list");
        else 
            // note that the list copy is in 
            // the constructor
            return new SimpleList<E>(list.next);
    }
    private ListNode<E> copyNodes(ListNode<E> l) {
        if (l == null)
            return null;
        else 
            return new ListNode<E>(l.element, copyNodes(l.next));
    }
    /**
     * Test if the list is logically empty.
     * @return true if empty, false otherwise.
     */
    public boolean isEmpty(){ return list == null; }
    /**
     * Make the list logically empty.
     */
    public void makeEmpty() { list = null; }
    /**
      @return A String representation of the list
     */
    public String toString() {
        String s = "[";
        try{
            if (!this.isEmpty())
                s += getString(this.head()) +
                    this.tail().toString_Nodes();
        } catch (ItemNotFound e) {};
        return s + "]";
    }
    private String toString_Nodes(){
        String s = "";
        try{
            if (!this.isEmpty())
                s += "," + getString(this.head()) + 
                    this.tail().toString_Nodes();
        } catch (ItemNotFound e) {};
        return s;
    }
    private String getString(Object obj) {
        return (obj == null ? "null" : obj.toString());
    }
    //=============================================
     private class ListNode<E> {

        E element;
        ListNode<E> next;

        ListNode( E theElement ) {
            this( theElement, null );
        }

        ListNode( E theElement, ListNode<E> n ) {
            element = theElement;
            next    = n;
        }
    }

}

///////////////////////////////////////////////

class ItemNotFound extends RuntimeException {

    public ItemNotFound( String message ) {
        super( message );
    }

}

	public static boolean member(Integer obj,SimpleList<Integer> l);
	// returns true if obj is a member of l, false otherwise
	{
		if(l.isEmpty());
			return false;
		else ()
	}