If you start a new document, there are no styles defined. Either start from an existing template and copy the styles, or create your own (like I did, based on https://stackoverflow.com/a/27864752/461499 )
See here:
XWPFDocument document = new XWPFDocument();
XWPFStyles styles = document.createStyles();
String heading1 = "My Heading 1";
String heading2 = "My Heading 2";
String heading3 = "My Heading 3";
String heading4 = "My Heading 4";
addCustomHeadingStyle(document, styles, heading1, 1, 36, "4288BC");
addCustomHeadingStyle(document, styles, heading2, 2, 28, "4288BC");
addCustomHeadingStyle(document, styles, heading3, 3, 24, "4288BC");
addCustomHeadingStyle(document, styles, heading4, 4, 20, "000000");
XWPFParagraph paragraph = document.createParagraph();
paragraph.setStyle(heading1);
XWPFRun run = paragraph.createRun();
run.setText("Nice header!");
And
private static void addCustomHeadingStyle(XWPFDocument docxDocument, XWPFStyles styles, String strStyleId, int headingLevel, int pointSize, String hexColor) {
CTStyle ctStyle = CTStyle.Factory.newInstance();
ctStyle.setStyleId(strStyleId);
CTString styleName = CTString.Factory.newInstance();
styleName.setVal(strStyleId);
ctStyle.setName(styleName);
CTDecimalNumber indentNumber = CTDecimalNumber.Factory.newInstance();
indentNumber.setVal(BigInteger.valueOf(headingLevel));
// lower number > style is more prominent in the formats bar
ctStyle.setUiPriority(indentNumber);
CTOnOff onoffnull = CTOnOff.Factory.newInstance();
ctStyle.setUnhideWhenUsed(onoffnull);
// style shows up in the formats bar
ctStyle.setQFormat(onoffnull);
// style defines a heading of the given level
CTPPr ppr = CTPPr.Factory.newInstance();
ppr.setOutlineLvl(indentNumber);
ctStyle.setPPr(ppr);
XWPFStyle style = new XWPFStyle(ctStyle);
CTHpsMeasure size = CTHpsMeasure.Factory.newInstance();
size.setVal(new BigInteger(String.valueOf(pointSize)));
CTHpsMeasure size2 = CTHpsMeasure.Factory.newInstance();
size2.setVal(new BigInteger("24"));
CTFonts fonts = CTFonts.Factory.newInstance();
fonts.setAscii("Loma" );
CTRPr rpr = CTRPr.Factory.newInstance();
rpr.setRFonts(fonts);
rpr.setSz(size);
rpr.setSzCs(size2);
CTColor color=CTColor.Factory.newInstance();
color.setVal(hexToBytes(hexColor));
rpr.setColor(color);
style.getCTStyle().setRPr(rpr);
// is a null op if already defined
style.setType(STStyleType.PARAGRAPH);
styles.addStyle(style);
}
public static byte[] hexToBytes(String hexString) {
HexBinaryAdapter adapter = new HexBinaryAdapter();
byte[] bytes = adapter.unmarshal(hexString);
return bytes;
}
