001    package com.thaiopensource.validate.mns;
002    
003    import java.util.Hashtable;
004    
005    class Hashset {
006      private final Hashtable table = new Hashtable();
007    
008      boolean contains(Object key) {
009        return table.get(key) != null;
010      }
011    
012      void add(Object key) {
013        table.put(key, key);
014      }
015    
016      void clear() {
017        table.clear();
018      }
019    }