Linked Stack Of Strings.java

LinkedStackOfStrings.java

public class LinkedStackOfStrings

{

    private int N;         

    private Node first;    

    private class Node

   {

        private String item;

        private Node next;

    }

                public boolean isEmpty()

    {

        return first == null;

    }

                 public int size()

                {

                      return N;

                }

              public void push(String item)

               {

        Node oldfirst = first;

        first = new Node();

        first.item = item;

        first.next = oldfirst;

        N++;

    }

        public String pop()

       {

        if (isEmpty()) throw new RuntimeException("Stack underflow");

        String item = first.item;     

        first = first.next;           

        N--;

        return item;                  

        }

    public static void main(String[] args)

    {

        int max = Integer.parseInt(args[0]);

        LinkedStackOfStrings s = new LinkedStackOfStrings();

        while (!StdIn.isEmpty())

       {

            String item = StdIn.readString();

            if (!item.equals("-"))

         s.push(item);

            else if (s.isEmpty()) 

        StdOut.println("BAD INPUT");

            else                  

        StdOut.print(s.pop());

        }

    }

            }