How to insert a linebreak as the data of a cell using Apache POI?

Try this: here

Row row = sheet.createRow(2);
Cell cell = row.createCell(2);
cell.setCellValue("Use \n with word wrap on to create a new line");

//to enable newlines you need set a cell styles with wrap=true
CellStyle cs = wb.createCellStyle();
cs.setWrapText(true);
cell.setCellStyle(cs);