code: public boolean containsKey(Object key) {
      FastHashtableEntry tab[] = table;
      int hash = key.hashCode();
      int index = (hash & 0x7FFFFFFF) % tab.length;
      for (FastHashtableEntry e = tab[index] ; e != null ; e = e.next) {
        if ((e.hash == hash) && e.key.equals(key)) {
          return true;
        }
      }
      return false;
    }
docs: Tests if the specified object is a key in this hashtable.
  
  @param   key   possible key.
  @return  <code>true</code> if the specified object is a key in this
  hashtable; <code>false</code> otherwise.
  @see     java.util.Hashtable#contains(java.lang.Object)
  @since   JDK1.0