The JCopyBookConverter.readCopyBookAsJDataFrameBuilder method from the RCOBOLDI package with the JAMon monitor and log invocations removed for brevity.

ReadCopyBookAsJDataFrameBuilderExample.java

private JDataFrameBuilder<String, String[]> readCopyBookAsJDataFrameBuilder(
    AbstractLineReader reader,
    LayoutDetail layout,
    String font,
    IUpdateFieldName updateFldName
) throws IOException {

    JDataFrameBuilder<String, String[]> result =
        new JDataFrameBuilder<String, String[]>(
            new JDataFrame<String, String[]>(),
                new RemoteAdapter<String, String[]>()
        );

    AbstractLine line;

    RecordDetail rec = layout.getRecord(0);

    for (int ctr = 1; ctr < rec.getFieldCount(); ctr++) {

        var header = (updateFldName.updateName(rec.getField(ctr).getName()));

        result.getDataFrame().addOrReturnExistingColumn(header);
    }

    int idx;

    while ((line = reader.read()) != null) {

        idx = line.getPreferredLayoutIdx();

        if (0 <= idx) {

            for (int ctr = 1; ctr < layout.getRecord(idx).getFieldCount(); ctr++) {

                var header = rec.getField(ctr).getName();

                var value = line.getFieldValue(idx, ctr);

                var formattedValue = (String) null;

                if (value != null && !(value.isSpaces() || value.isLowValues() || value.isHighValues()) && value.isFieldPresent())
                    formattedValue = value.asString();

                result
                    .getDataFrame()
                    .addOrReturnExistingColumn(header)
                    .addValues(new String[]{formattedValue});
            }
        }
    }

    return result;
}