class Node {
   Object element;
   Node next;

   public Node(Object o, Node next) {
      this.element = o;
      this.next = next;
   }

// Let's skip all the set and get methods to keep it short

} 



public class SinglyLinkedList {

   Node head;

// constructor creates an empty list

   public SinglyLinkedList () {
      head = null;
   }

// a method to insert at the head of the list

   public void insert(Object o){
      Node newHead = new Node(o, head);
      head = newHead;
   }

// a method to remove the head of the list

   public void remove(){
      if (head == null) return;

      else head = head.next;
   }

// a method to check if the list contains an element o

   public boolean contains (Object o) {
      if (head == null) return false;
      if (head.element.equals(o)) return true;
      Node current = head;
      while (current.next != null) {
         current = current.next;
         if (current.element.equals(o)) return true;
      }
      return false;
   }

   public Object get(int i) throws BadIndexException {
      if (i < 0 ) throw new BadIndexException();
      if (head == null) throw new BadIndexException();
      if (i == 0) return head.element;
      Node current = head;
      while (current.next != null) {
         current = current.next;
         i--;
         if (i == 0) return current.element;
      }
      throw new BadIndexException();
   }

    // just for illustration;

   public static void main (String[] args)  throws BadIndexException { 
      SinglyLinkedList l = new SinglyLinkedList();
      String[] numbers = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};
      System.out.println("Adding ten numbers");
      for (int i = 0; i < numbers.length; i++) {
         l.insert(numbers[i]);
      }

      Node current = l.head;
      while (current != null) {
         System.out.print(current.element + " ");
         current = current.next;
      }
      System.out.println();
      System.out.println("Does it contain 0?");
      System.out.println(l.contains("0"));
      System.out.println("What is the element at  rank 9?");
      System.out.println(l.get(9));
      System.out.println("Removing head");
      l.remove(); 
      current = l.head;
      while (current != null) {
         System.out.print(current.element + " ");
         current = current.next;
      }
      System.out.println();
      System.out.println("What is the element at  rank 9?");
      System.out.println(l.get(9));
   } 

}
            
class BadIndexException extends Exception {

}