如何导入 Excel 中的 JTable 值？

Question

我正在尝试在 excel sheet 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 循环之后使用 break 插入该数据时，它将把它插入到 excel 但其他它会给出空指针异常。

代码如下：

 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);
        }
    }

代码中的错误在行 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.access00(DataEntryArea.java:87)
        at com.boolment.dataentry.DataEntryArea.actionPerformed(DataEntryArea.java:717)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
        at java.awt.Component.processMouseEvent(Component.java:6533)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
        at java.awt.Component.processEvent(Component.java:6298)
        at java.awt.Container.processEvent(Container.java:2236)
        at java.awt.Component.dispatchEventImpl(Component.java:4889)
        at java.awt.Container.dispatchEventImpl(Container.java:2294)
        at java.awt.Component.dispatchEvent(Component.java:4711)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
        at java.awt.Container.dispatchEventImpl(Container.java:2280)
        at java.awt.Window.dispatchEventImpl(Window.java:2746)
        at java.awt.Component.dispatchEvent(Component.java:4711)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
        at java.awt.EventQueue.access0(EventQueue.java:97)
        at java.awt.EventQueue.run(EventQueue.java:709)
        at java.awt.EventQueue.run(EventQueue.java:703)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
        at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
        at java.awt.EventQueue.run(EventQueue.java:731)
        at java.awt.EventQueue.run(EventQueue.java:729)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$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，但仍然无法正常工作。我该如何解决？

Answer 1

我找到了获取空指针异常的解决方案。由于此 datatypetable.getValueAt(i, j).toString() 我收到错误，因为某些值 table 可能为空，当它们为空时出现错误 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，因为上面的代码和我问的一样。唯一的变化是在这个 for 循环中进行。希望我的回答对大家有帮助。

如何导入 Excel 中的 JTable 值？

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