java - 如何解决 java.lang.ClassCastException 错误

Question

我在 swing eclipse 的 JTable 属性中设计了默认表模型。所以当我尝试进行计算时出现错误......线程“AWT-EventQueue-0”中的异常java.lang.ClassCastException:java.lang.String无法转换为java.lang.Integer

public class punchingPBill extends JFrame
{
    DefaultTableModel model;
    Double rate,discount,amount,exciseduty,outputvat;

    {
        String[] columnNames =  {"Sr.No", "Description Of Goods", "quantity", "Rate", "Per", "Discount", "Basic Excise Duty", "Output Vat", "Amount"};
        Object[][] data = { {new Integer(1),"",new Integer(1), new Double(0.0),new Double(0.0),new Double(0.0),new Double(0.0),new Double(0.0),new Double(0.0)}};

    model = new DefaultTableModel(data, columnNames);
    }       
        table.setModel(model);
        table.setRowHeight(25);

private void setTableModelListener()
    {
        System.out.println("enter listen");
        TableModelListener tableModelListener = new TableModelListener() 
{
         public void tableChanged(TableModelEvent e)
            {
               if (e.getType() == TableModelEvent.UPDATE)
                {
                    System.out.println("Cell " + e.getFirstRow() + ", "
                            + e.getColumn() + " changed. The new value: "
                            + table.getModel().getValueAt(e.getFirstRow(),
                                    e.getColumn()));
                    int row = e.getFirstRow();
                    int column = e.getColumn();

                    if(column == 2||column == 3||column == 5)
                    {
                     Integer    quantity = ((Integer) model.getValueAt(row, 2)).intValue();
                   rate = ((Double) model.getValueAt(row, 3)).doubleValue(); 
                   discount=((Double) model.getValueAt(row, 5)).doubleValue();
                   amount=new Double(rate-(quantity*rate*(discount/100)));

                   model.setValueAt(amount, row, 8);

                 }

                }
            }
        };
        table.getModel().addTableModelListener(tableModelListener);
}

在 - 整数数量 = ((Integer) model.getValueAt(row, 2)).intValue();......rate = ((Double) model.getValueAt(row, 3)) 处出现错误.doubleValue();......discount=((Double) model.getValueAt(row, 5)).doubleValue();

Answer 1

您可以使用 Integer.parseInt("StringValue") 代替强制转换，其中“StringValue”应该是可以转换为整数的适当数值