小编Tsa*_*sar的帖子

我正在尝试从select语句返回一个值.它只有一个值,因为我返回的值来自主键列.

SQL语句是 SELECT itemNo FROM item WHERE itemName = 'astringvalue';

我获取值的方法如下所示:

private String viewValue(Connection con, String command) throws SQLException 
    {
        String value = null;
        Statement stmt = null;

        try 
        {
            stmt = con.createStatement();
            ResultSet rs = stmt.executeQuery(command);

            while (rs.next())
                value = rs.toString();
        } 

        catch (SQLException e ) 
        {
            e.printStackTrace();
        } 

        finally
        {
            if (stmt != 
            null) { stmt.close(); }
        }

        return value;

    }

我也有一个getConnection()方法.

这是我用来调用viewValue方法的方法:

if((action.getSource() == btnSave) ||(action.getSource() == btnSavePrint) )
        {
            String findItemNoCommand = …

我尝试运行以下代码.它编译,但抛出ClassCastException.如果有人能帮助我找出原因,我会很高兴的.

double costprice = 0;
Object[] possibilities = null;
costprice = (double) JOptionPane.showInputDialog(
                    alphaPOS,
                    "Cost Price:",
                    "Enter Values",
                    JOptionPane.PLAIN_MESSAGE,
                    null,
                    possibilities,
                    "");