import java.util.*;

public class MyTestMap
{
   public static void main(String[] args) 
   {
      int i;
      Integer freq;
      String s;

      HashMap M = new HashMap(4);

      M.put("a", 1);
      System.out.println(M);
      M.put("b", 1);
      System.out.println(M);
      M.put("c", 1);
      System.out.println(M);
      M.put("d", 1);
      System.out.println(M);
      M.put("e", 1);
      System.out.println(M);

      M.remove("a");
      System.out.println(M);
      M.remove("b");
      System.out.println(M);
      M.put("e", 1);
      System.out.println(M);

      System.out.println(M.size() + " words");

     Collection<String> c = M.keySet();

      /* ------------------------------------------------
         Get an iterator over a Set
         ----------------------------------------------- */
      Iterator iter = c.iterator();

      /* -------------------------
         Iterate over "iter"
         ------------------------- */
      while(iter.hasNext())
      {
         String x;    // Help variable
 
         x = (String) iter.next();              // Get next entry      

         System.out.println(x);
      }
      System.out.println();

   }
}