Create a table in powerpoint with Apache poi - apache-poi

Question

I'm using Java v8 and "org.apache.poi" and "poi-ooxml" (both are version 3.9). I'm trying to create a powerpoint with a slide on it which contains a table.
I can get the powerpoint file to create ok but the slide is empty but for a small black box in the top right corner. I'm guessing I'm missing something small but can't see what it is. I've tried some examples from the web and they look to be the same as what I'm seeing.
This is what I see in the Powerpoint slide:
My code is as below:
XMLSlideShow powerpoint = new XMLSlideShow();
XSLFSlide slide = powerpoint.createSlide();
XSLFTable table = slide.createTable();
table.setAnchor(new Rectangle(50, 50, 800, 800));
int numColumns = 3;
int numRows = 5;
XSLFTableRow headerRow = table.addRow();
headerRow.setHeight(50);
// header
for (int i = 0; i < numColumns; i++) {
XSLFTableCell th = headerRow.addCell();
XSLFTextParagraph p = th.addNewTextParagraph();
p.setTextAlign(TextAlign.CENTER);
XSLFTextRun r = p.addNewTextRun();
r.setText("Header " + (i + 1));
r.setFontSize(20);
r.setFontColor(Color.white);
th.setFillColor(new Color(79, 129, 189));
table.setColumnWidth(i, 150);
}
// rows
for (int rownum = 0; rownum < numRows; rownum++) {
XSLFTableRow tr = table.addRow();
tr.setHeight(50);
// header
for (int i = 0; i < numColumns; i++) {
XSLFTableCell cell = tr.addCell();
XSLFTextParagraph p = cell.addNewTextParagraph();
XSLFTextRun r = p.addNewTextRun();
r.setText("Cell " + (i + 1));
if (rownum % 2 == 0) {
cell.setFillColor(new Color(208, 216, 232));
}
else {
cell.setFillColor(new Color(233, 247, 244));
}
}
}
try {
try (FileOutputStream out = new FileOutputStream("c:\\myFile.pptx"))
{
try {
powerpoint.write(out);
} catch (IOException e) {
e.printStackTrace();
}
}
} catch (IOException e) {
e.printStackTrace();
}
Any thoughts/guidance would be really appreciated.
Thanks Ro