How to create a nested column?

I need help creating a nested table in iText.

How can I create a table that looks like the table in the following screen shot:

This is my code so far:

var subTable2 = new PdfPTable(new float[] { 100, 100, 100, 100, 100, 100,100,100 });
subTable2.TotalWidth = 510f;
subTable2.LockedWidth = true;
subTable2.DefaultCell.HorizontalAlignment = Element.ALIGN_CENTER;
subTable2.AddCell(new Phrase("Examination", time51));
subTable2.DefaultCell.HorizontalAlignment = Element.ALIGN_CENTER;
subTable2.AddCell(new Phrase("Board", time51));
subTable2.DefaultCell.HorizontalAlignment = Element.ALIGN_CENTER;
subTable2.AddCell(new Phrase("Month and Year of Passing", time51));
subTable2.DefaultCell.HorizontalAlignment = Element.ALIGN_CENTER;
subTable2.AddCell(new PdfPCell(new Phrase("Mark", time51)));
PdfPTable nested = new PdfPTable(1);
nested.AddCell("");
nested.AddCell("Obtained");
nested.AddCell("Out of");
PdfPCell nesthousing = new PdfPCell(nested);
nesthousing.Padding = 0f;
subTable2.AddCell(nesthousing);
subTable2.DefaultCell.HorizontalAlignment = Element.ALIGN_CENTER;
subTable2.AddCell(new Phrase("Percentage", time51));
subTable2.DefaultCell.HorizontalAlignment = Element.ALIGN_CENTER;
subTable2.AddCell(new Phrase("Calss/Grade", time51));
doc.Add(subTable2);

Please take a look at SimpleTable12. It creates a table that looks like this: simple_table12.pdf

Table example

You could still fine-tune the height of the cells by using a padding, but those are details. What matters is: how to organize the cells?

I've written this small convenience method:

public Cell createCell(String content, int colspan, int rowspan, int border) {
    Cell cell = new Cell(rowspan, colspan).add(new Paragraph(content));
    cell.setBorder(null);
    if (8 == (border & 8)) {
        cell.setBorderRight(new SolidBorder(1));
        cell.setBorderBottom(new SolidBorder(1));
    }
    if (4 == (border & 4)) {
        cell.setBorderLeft(new SolidBorder(1));
    }
    if (2 == (border & 2)) {
        cell.setBorderBottom(new SolidBorder(1));
    }
    if (1 == (border & 1)) {
        cell.setBorderTop(new SolidBorder(1));
    }
    return cell;
}

You pass some content, a colspan, a rowspan and border info and it creates you the Cell you need. This allows us to create code that is easier to read:

public void createPdf(String dest) throws Exception {
    PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
    Document doc = new Document(pdfDoc, PageSize.A4.rotate());

    font = PdfFontFactory.createFont(FontConstants.HELVETICA);
    Table table = new Table(8);

    table.setTextAlignment(TextAlignment.CENTER);
    table.setFont(font).setFontSize(10);

    table.addCell(createCell("Examination", 1, 2, 15));
    table.addCell(createCell("Board", 1, 2, 15));
    table.addCell(createCell("Month and Year of Passing", 1, 2, 15));
    table.addCell(createCell("", 1, 1, 1));
    table.addCell(createCell("Marks", 2, 1, 1));
    table.addCell(createCell("Percentage", 1, 2, 15));
    table.addCell(createCell("Class / Grade", 1, 2, 15));
    table.addCell(createCell("", 1, 1, 15));
    table.addCell(createCell("Obtained", 1, 1, 15));
    table.addCell(createCell("Out of", 1, 1, 15));
    table.addCell(createCell("12th / I.B. Diploma", 1, 1, 15));
    table.addCell(createCell("", 1, 1, 15));
    table.addCell(createCell("", 1, 1, 15));
    table.addCell(createCell("Aggregate (all subjects)", 1, 1, 15));
    table.addCell(createCell("", 1, 1, 15));
    table.addCell(createCell("", 1, 1, 15));
    table.addCell(createCell("", 1, 1, 15));
    table.addCell(createCell("", 1, 1, 15));

    doc.add(table);
    doc.close();
}

As you can see, it's a matter of calculating the correct colspan and rowspan values, and applying the correct borders.

Click this link if you want to see how to answer this question in iText 5.