Created attachment 35728 [details] test-File like the original code that causes the bug: public void dateiSpeichern(){ try (FileOutputStream outPutStream = new FileOutputStream(actualFile)){ System.out.println("File: "+actualFile); System.out.println("Sheet: "+actualSheet.getSheetName()); //Daten abspeichern Header header=actualSheet.getHeader(); header.setLeft(jtaZeitraum.getText()); header.setCenter(jtaAnschrift.getText());; header.setRight(jtaVonBis.getText()); for(int i=0; i<datensatzListe.size(); i++){ XSSFRow row=actualSheet.getRow(i+3); System.out.println("Row: "+row.getRowNum()); XSSFCell cell0=row.getCell(0); cell0.setCellValue(""); XSSFCell cell1=row.getCell(1); cell1.setCellValue(""); XSSFCell cell2=row.getCell(2); cell2.setCellValue(""); XSSFCell cell3=row.getCell(3); cell3.setCellValue(""); XSSFCell cell4=row.getCell(4); cell4.setCellValue(""); XSSFCell cell5=row.getCell(5); cell5.setCellValue(""); XSSFCell cell6=row.getCell(6); cell6.setCellValue(""); XSSFCell cell7=row.getCell(7); cell7.setCellValue(""); XSSFCell cell8=row.getCell(8); cell8.setCellValue(""); XSSFCell cell9=row.getCell(9); cell9.setCellValue(""); XSSFCell cell10=row.getCell(10); cell10.setCellValue(""); } for(int i=0; i<datensatzListe.size(); i++){ XSSFRow row=actualSheet.getRow(i+3); System.out.println("Row: "+row.getRowNum()); XSSFCell cell0=row.getCell(0); System.out.println("Cell: "+cell0.getColumnIndex()); cell0.setCellValue(datensatzListe.get(i).getEinnahmen()); XSSFCell cell1=row.getCell(1); cell1.setCellValue(datensatzListe.get(i).getMwstEin()); XSSFCell cell2=row.getCell(2); cell2.setCellValue(datensatzListe.get(i).getAusgaben()); XSSFCell cell3=row.getCell(3); cell3.setCellValue(datensatzListe.get(i).getMwst19Aus()); XSSFCell cell4=row.getCell(4); cell4.setCellValue(datensatzListe.get(i).getMwst7Aus()); XSSFCell cell5=row.getCell(5); cell5.setCellValue(datensatzListe.get(i).getRechnr()); XSSFCell cell6=row.getCell(6); cell6.setCellValue(datensatzListe.get(i).getZaehler()); XSSFCell cell7=row.getCell(7); cell7.setCellValue(datensatzListe.get(i).getDate()); XSSFCell cell8=row.getCell(8); cell8.setCellValue(datensatzListe.get(i).getVonFuer()); XSSFCell cell9=row.getCell(9); cell9.setCellValue(datensatzListe.get(i).getRubrik()); XSSFCell cell10=row.getCell(10); cell10.setCellValue(datensatzListe.get(i).getKonto()); } tabelleAktualisieren(); actualWB.write(outPutStream); outPutStream.flush(); outPutStream.close(); writerEx.flushFileWriter(); } catch (IOException e) { e.printStackTrace(); writerEx.printIOException(e); } catch (NullPointerException e1) { e1.printStackTrace(); writerEx.printNullPointerException(e1); } catch (Exception e2) { e2.printStackTrace(); writerEx.printException(e2); }finally{ } } The exception: java.lang.NullPointerException at gui.Reiter.dateiSpeichern(Reiter.java:576) at gui.Hauptfenster$4.actionPerformed(Hauptfenster.java:405) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.AbstractButton.doClick(AbstractButton.java:376) at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833) at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877) at java.awt.Component.processMouseEvent(Component.java:6533) at javax.swing.JComponent.processMouseEvent(JComponent.java:3324) at java.awt.Component.processEvent(Component.java:6298) at java.awt.Container.processEvent(Container.java:2236) at java.awt.Component.dispatchEventImpl(Component.java:4889) at java.awt.Container.dispatchEventImpl(Container.java:2294) at java.awt.Component.dispatchEvent(Component.java:4711) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466) at java.awt.Container.dispatchEventImpl(Container.java:2280) at java.awt.Window.dispatchEventImpl(Window.java:2746) at java.awt.Component.dispatchEvent(Component.java:4711) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758) at java.awt.EventQueue.access$500(EventQueue.java:97) at java.awt.EventQueue$3.run(EventQueue.java:709) at java.awt.EventQueue$3.run(EventQueue.java:703) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90) at java.awt.EventQueue$4.run(EventQueue.java:731) at java.awt.EventQueue$4.run(EventQueue.java:729) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80) at java.awt.EventQueue.dispatchEvent(EventQueue.java:728) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) at java.awt.EventDispatchThread.run(EventDispatchThread.java:82) Thanks for checking this problem! Best Regards Markus
There doesn't seem to be any Apache POI code involved in your stacktrace. Therefore, it rather seems to be a bug in your code... Can you write a short junit unit test case (or similar standalone program) which shows the issue to be in POI?
Created attachment 35730 [details] my short standalone program and my xlsxFile Hi, with this short JavaFile with the code I got the following exception: java.lang.NullPointerException at gui.WriteWorkbook.write(WriteWorkbook.java:42) at gui.WriteWorkbook.<init>(WriteWorkbook.java:22) at gui.WriteWorkbook.main(WriteWorkbook.java:113) Best regards Markus
Markus - the NullPointerException is in your code, not in Apache POI. Line 42 in your code is cell0=row.getCell(0); So most likely the row is null. I opened the xlsx file in your zip and the sheet called `test` is empty - which might explain why getRow for that sheet is returning null.