Question

我正在尝试在Excel工作表中加载JTable值，但它给出了空指针异常。现在，当我尝试在j的for循环后使用break插入数据时，会将其插入excel，而Other则将其提供Null Pointer Exception。

下面是代码：

 private void writeToExcel() {
        XSSFWorkbook ws = new XSSFWorkbook();
        XSSFSheet wb = ws.createSheet();
        XSSFRow row = wb.createRow(0);;
        XSSFCell cell = null;

        for (int i = 0; i < datatypetable.getRowCount(); i++) {
        int ColNum = 0;
        row = wb.createRow(i);
        for (int j = 0; j < datatypetable.getColumnCount(); j++) {
            cell = wb.getRow(i).getCell(ColNum, Row.MissingCellPolicy.CREATE_NULL_AS_BLANK);
            if (cell == null) {
                System.out.println("Cell Project is: " + cell.toString());  
                cell = row.createCell(ColNum);
                cell.setCellValue(datatypetable.getValueAt(i, j).toString());
            } else {
                //cell = row.createCell(j);  
                System.out.println("Cell Object is: " + cell.toString());  
                System.out.println(datatypetable.getValueAt(i, j).toString());
                **cell.setCellValue(datatypetable.getValueAt(i, j).toString());**
            }
            ColNum++;
        }

    }    

        //Write Excel to file System
        try {
            FileOutputStream fos = new FileOutputStream(workingDir + File.separator + "First" + ".xls");
            ws.write(fos);
            fos.close();
        } catch (FileNotFoundException ex) {
            Logger.getLogger(DataEntryArea.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(DataEntryArea.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

代码中的错误位于 cell.setCellValue（datatypetable.getValueAt（i，j）.toString（））; -

   Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at com.boolment.dataentry.DataEntryArea.writeToExcel(DataEntryArea.java:1243)
        at com.boolment.dataentry.DataEntryArea.jButton6ActionPerformed(DataEntryArea.java:1263)
        at com.boolment.dataentry.DataEntryArea.access$2000(DataEntryArea.java:87)
        at com.boolment.dataentry.DataEntryArea$23.actionPerformed(DataEntryArea.java:717)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
        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)

我知道此代码有一个解决方案，我也尝试过这样做，但仍然无法正常工作。我该如何解决呢？

Answer 1

我已经找到了获取空指针异常的解决方案。由于此datatypetable.getValueAt(i, j).toString()，我收到了错误信息，因为table的某些值可能为null，而当它们为null时，它会收到错误NullPointerException。

for (int i = 0; i < datatypetable.getRowCount(); i++) {
                int ColNum = 0;
                row = wb.createRow(i);
                for (int j = 0; j < datatypetable.getColumnCount(); j++) {
                    cell = wb.getRow(i).getCell(ColNum, Row.MissingCellPolicy.CREATE_NULL_AS_BLANK);
                    String item1 = null;
                    if (datatypetable.getValueAt(i, j) != null) {
                        cell.setCellValue(datatypetable.getValueAt(i, j).toString());
                    } else {
                        cell.setCellValue(item1);
                    }
                    ColNum++;
                }


   }

我没有提供完整的代码，因为上述代码与我要求的相同。唯一的更改是在此for循环中进行的。希望我的回答对任何人有帮助。

如何在Excel中导入JTable值？

1 个答案: