public static List<Ryhma> getRyhmat() {
		Connection c = connect();
		if (c == null) return null;
		try {
			List<Ryhma> ryhmat = new ArrayList<Ryhma>();
			PreparedStatement ps = c.prepareStatement("SELECT * FROM ryhma;");

			ResultSet rs = ps.executeQuery();
			while (rs.next()) {
				ryhmat.add(ryhmaResultSetista(rs));
			}

			return ryhmat;
		} catch (SQLException e) {
			return null;
		} finally {
			closeConnection(c);
		}
	}