public class ExportExcel {

private static String getCellValue(JTable table, int x, int y) {
return table.getValueAt(x, y).toString();
}

public static void writeToExcel (JTable table) {
XSSFWorkbook wb = new XSSFWorkbook();
XSSFSheet ws = wb.createSheet();
TreeMap<String, Object[]> data = new TreeMap<>();
data.put("-1", new Object[]{table.getColumnName(0), table.getColumnName(1)});
for (int i = 0; i < table.getRowCount(); i++) {
data.put(Integer.toString(i), new Object[] {getCellValue(table, i, 0), getCellValue(table, i, 1)});
}
Set<String> ids = data.keySet();
XSSFRow row;
int rowId = 0;
for (String key: ids) {
row = ws.createRow(rowId++);
Object[] values = data.get(key);
int celId=0;
for (Object o: values) {
Cell cell = row.createCell(celId++);
cell.setCellValue(o.toString());
}
}

try {
FileOutputStream fos = new FileOutputStream(new File("D:\\EXCEL.xlsx"));
wb.write(fos);
fos.close();
} catch (Exception Ex) {
Logger.getLogger(ExportExcel.class.getName()).log(Level.SEVERE, null, Ex);
new errorDialog(null, new StringEntered(Ex.getMessage()).getStringEntered(100),
new StringEntered().toString(Ex.getStackTrace()), "Программная ошибка", JOptionPane.ERROR_MESSAGE);
}
}