BST in a java programe

BST.java

import java.util.Iterator;

import java.util.NoSuchElementException;

public class BST, Val> implements Iterable

 {

    private Node root;         

    private int N;             

    private class Node

       {

        private Key key;             

        private Val val;             

        private Node left, right;    

        Node(Key key, Val val)

       {

            this.key = key;

            this.val = val;

            N++;

        }

    }

    public BST()

   {

        root = null;

        N = 0;

    }

    public int size()

     {

        return N;

     }

    public void put(Key key, Val value)

   {

        if (value == null) delete(key);

        root = insert(root, key, value);

    }

    private Node insert(Node x, Key key, Val value)

   {

        if (x == null) return new Node(key, value);

        int cmp = key.compareTo(x.key);

        if      (cmp < 0) x.left  = insert(x.left,  key, value);

        else if (cmp > 0) x.right = insert(x.right, key, value);

        else x.val = value;

        return x;

    }

    public boolean contains(Key key)

   {

        return get(key) != null;

    }

    public Val get(Key key)

   {

        Node x = root;

        while (x != null)

    {

            int cmp = key.compareTo(x.key);

            if      (cmp < 0) x = x.left;

            else if (cmp > 0) x = x.right;

            else return x.val;

        }

        return null;

    }

    public void delete(Key key)

   {

        throw new RuntimeException("Deletion operation not supported");

    }

    public Iterator iterator()

   {

          return new Inorder();

    }

                private class Inorder implements Iterator

     {

        private Stack stack = new Stack();

        Inorder()

         {

      pushLeft(root);

      }

                  public void remove()     

       {

              throw new UnsupportedOperationException(); 

        }

        public boolean hasNext() 

        {

           return !stack.isEmpty();                

        }

        public Key next()

       {

            if (!hasNext()) throw new NoSuchElementException();

            Node x = stack.pop();

            pushLeft(x.right);

            return x.key;

        }

        public void pushLeft(Node x)

       {

            while (x != null)

       {

                stack.push(x);

                x = x.left;

            }

        }

    }

    public static void main(String[] args)

   {

        BST st = new BST();

       

        st.put("www.cs.princeton.edu",   "128.112.136.11");

        st.put("www.cs.princeton.edu",   "128.112.136.35");   

        st.put("www.princeton.edu",      "128.112.130.211");

        st.put("www.math.princeton.edu", "128.112.18.11");

        st.put("www.yale.edu",           "130.132.51.8");

        st.put("www.amazon.com",         "207.171.163.90");

        st.put("www.simpsons.com",       "209.123.16.34");

        st.put("www.stanford.edu",       "171.67.16.120");

        st.put("www.google.com",         "64.233.161.99");

        st.put("www.ibm.com",            "129.42.16.99");

        st.put("www.apple.com",          "17.254.0.91");

        st.put("www.slashdot.com",       "66.35.250.150");

        st.put("www.whitehouse.gov",     "204.153.49.136");

        st.put("www.espn.com",           "199.181.132.250");

        st.put("www.snopes.com",         "66.165.133.65");

        st.put("www.movies.com",         "199.181.132.250");

        st.put("www.cnn.com",            "64.236.16.20");

        st.put("www.iitb.ac.in",         "202.68.145.210");

                StdOut.println("size = " + st.size());

        StdOut.println(st.get("www.cs.princeton.edu"));

        StdOut.println(st.get("www.amazon.com"));

        StdOut.println(st.get("www.amazon.edu"));

        StdOut.println();

        for (String s : st)  

       {

            StdOut.println(s);

        }

    }

}