import java.util.*;

class ETable4 implements ETable
{
// Table class, data stored in hash table
// Handles collisions with linear probing
// Returns an Enumeration

 private KeyObject[] array;
 final static int SIZE=41;

 public ETable4()
 {
  array = new KeyObject[SIZE];
 }

 public boolean delete(String key)
 {
  int i = hash(key);
  while(array[i]!=null&&!array[i].equalKey(key))
     i=(i+1)%SIZE;
  if(array[i]==null)
     return false;
  else
     {
      array[i] = new Deleted();
      return true;
     }
 }

 public void add(KeyObject obj)
 {
  int i = hash(obj.getKey());
  while(array[i]!=null && !(array[i] instanceof Deleted))
     i=(i+1)%SIZE;
  array[i]=obj;
 }

 public KeyObject retrieve(String key)
 {
  int i = hash(key);
  while(array[i]!=null&&!array[i].equalKey(key))
     i=(i+1)%SIZE;
  return array[i];
 }

 public Enumeration getEnumeration()
 {
  return new MyEnumeration();
 }

 private static int hash(String key)
 {
  int val=0;
  key = key.toLowerCase();
  for(int i=0; i<key.length(); i++)
     if(Character.isLetter(key.charAt(i)))
        val=(val*32+key.charAt(i)-'a')%SIZE;
  return val;
 }

 private static class Deleted extends KeyObject
 {
  public String getKey()
  {
   return "";
  }
 }

 private class MyEnumeration implements Enumeration
 {
  int current;

  MyEnumeration()
  {
   current=-1;
   moveCurrent();
  }

  public boolean hasMoreElements()
  {
   return current<SIZE;
  }

  public Object nextElement()
  {
   Object obj = array[current];
   moveCurrent();
   return obj;
  }

  private void moveCurrent()
  {
   current++;
   while(current<SIZE&&
         (array[current]==null||array[current] instanceof Deleted))
      current++;
  }
 }
}