public void set_field( String section, String field, String data ) 
 throws NullPointerException {
	Hashtable s;
	
	if( section== null || field == null )
		throw new NullPointerException();

	s = (Hashtable) sections.get(section);

	if(s==null) {
		s = new Hashtable();
		sections.put(section, s);
	}

	s.put(field, data);
}