public void writeTo(OutputStream out) throws IOException {
		XmlOptions options = new XmlOptions(DEFAULT_XML_OPTIONS);

		// Work on the current one
		// Need to do this, as we don't handle
		//  all the possible entries yet
		CTStylesheet styleSheet = doc.getStyleSheet();

		// Formats
		CTNumFmts formats = CTNumFmts.Factory.newInstance();
		formats.setCount(numberFormats.size());
		for (Entry<Integer, String> fmt : numberFormats.entrySet()) {
			CTNumFmt ctFmt = formats.addNewNumFmt();
			ctFmt.setNumFmtId(fmt.getKey());
			ctFmt.setFormatCode(fmt.getValue());
		}
		styleSheet.setNumFmts(formats);

		int idx;
		// Fonts
		CTFonts ctFonts = styleSheet.getFonts();
		if (ctFonts == null) {
			ctFonts = CTFonts.Factory.newInstance();
		}
		ctFonts.setCount(fonts.size());
		CTFont[] ctfnt = new CTFont[fonts.size()];
		idx = 0;
		for(XSSFFont f : fonts) ctfnt[idx++] = f.getCTFont();
		ctFonts.setFontArray(ctfnt);
		styleSheet.setFonts(ctFonts);

		// Fills
		CTFills ctFills = styleSheet.getFills();
		if (ctFills == null) {
			ctFills = CTFills.Factory.newInstance();
		}
		ctFills.setCount(fills.size());
		CTFill[] ctf = new CTFill[fills.size()];
		idx = 0;
		for(XSSFCellFill f : fills) ctf[idx++] = f.getCTFill();
		ctFills.setFillArray(ctf);
		styleSheet.setFills(ctFills);

		// Borders
		CTBorders ctBorders = styleSheet.getBorders();
		if (ctBorders == null) {
			ctBorders = CTBorders.Factory.newInstance();
		}
		ctBorders.setCount(borders.size());
		CTBorder[] ctb = new CTBorder[borders.size()];
		idx = 0;
		for(XSSFCellBorder b : borders) ctb[idx++] = b.getCTBorder();
		ctBorders.setBorderArray(ctb);
		styleSheet.setBorders(ctBorders);

		// Xfs
		if(xfs.size() > 0) {
			CTCellXfs ctXfs = styleSheet.getCellXfs();
			if (ctXfs == null) {
				ctXfs = CTCellXfs.Factory.newInstance();
			}
			ctXfs.setCount(xfs.size());
			ctXfs.setXfArray(
					xfs.toArray(new CTXf[xfs.size()])
			);
			styleSheet.setCellXfs(ctXfs);
		}

		// Style xfs
		if(styleXfs.size() > 0) {
			CTCellStyleXfs ctSXfs = styleSheet.getCellStyleXfs();
			if (ctSXfs == null) {
				ctSXfs = CTCellStyleXfs.Factory.newInstance();
			}
			ctSXfs.setCount(styleXfs.size());
			ctSXfs.setXfArray(
					styleXfs.toArray(new CTXf[styleXfs.size()])
			);
			styleSheet.setCellStyleXfs(ctSXfs);
		}

		// Style dxfs
		if(dxfs.size() > 0) {
			CTDxfs ctDxfs = styleSheet.getDxfs();
			if (ctDxfs == null) {
				ctDxfs = CTDxfs.Factory.newInstance();
			}
			ctDxfs.setCount(dxfs.size());
			ctDxfs.setDxfArray(dxfs.toArray(new CTDxf[dxfs.size()])
			);
			styleSheet.setDxfs(ctDxfs);
		}

		// Save
		doc.save(out, options);
	}