import java.util.*;

/** Generic singly linked list with just a head */
public class GList<E> {
    
    private Node<E> head;  //head node of the list
		
    /** Default constructor that creates an empty list */
    public GList(){head = null;}
		
		
    /** return the head of the list */
    public Node<E> getHead(){return head;}
		
    /** set the head of the list */
    public void setHead(Node<E> node){head = node;}
		
		
    /** is the list empty? */
    public boolean isEmpty(){return head == null;}
		
    /** add a new node at front of list */
    public void addFirst(Node<E> node){
	node.setNext(head);
	head = node;
    }
		
    /** remove node from front of list */
    public void removeFirst(){
	if (!isEmpty()) head = head.getNext();
    }

    /** String representation of list */
    public String toString(){
	Node cursor = head;
	String s = "(";
	while(cursor != null){
	    s = s + cursor;
	    cursor = cursor.getNext();
	    if (cursor != null) s = s + ",";
	}
	return s + ")";
    }

    public Iterator<E> iterator(){
	GIterator<E> iter = new GIterator<E>(this);
	return (Iterator<E>) iter;
    }
}