public class LinkedList2 implements List
{
 private Object myhead;
 private LinkedList2 mytail;
 private boolean empty;

 private LinkedList2(Object h, LinkedList2 t)
 {
  myhead=h;
  mytail=t;
 }

 private LinkedList2()
 {
  empty=false;
 }

 public static List empty()
 {
  return new LinkedList2();
 }

 public List cons(Object o)
 {
  return new LinkedList2(o, new LinkedList2(myhead, mytail));
 }

  public boolean isempty()
  {
   return empty;
  }

  public Object head()
  {
   return myhead;
  }

 public List tail()
 {
  return mytail;
 }

 public String toString()
 {
  if(isempty())
     return "[]";
  else
     return "["+myhead.toString()+tailToString(mytail);
 }

 private static String tailToString(List L)
 {
  if(L.isempty())
     return "]";
  else
     return ","+L.head().toString()+tailToString(L.tail());
 }

}