Soma de uma tabela

try {

bancodados.CriaConexao.getConexao();

Connection conn = (Connection) CriaConexao.getConexao();

Statement stmt = (Statement) conn.createStatement();

String sql = "SELECT MAX( VALOR_TOTAL )FROM ITENS_COMPRA where COD_COMPRAS = "+jtcodCompra.getText();

System.out.println(sql);

ResultSet rs = stmt.executeQuery(sql);

rs.next();

double codigo = rs.getDouble(7);

System.out.println("aa: "+String.valueOf(codigo));

conn.close();

} catch (SQLException ex) {
        System.out.println("erro");
    }