我的学校作业遇到了问题，我们必须为一家快餐公司创建一个pos。作业的一部分是在输入投标金额后计算变更。我的问题是，由于“$”的原因，程序无法从投标金额中减去总金额。我的代码当前如下所示：

private void totalButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            

    // Finding the subtotal
            double burgers;
            double fries;
            double drinks;
            double subtotal;

            burgers = 2.49;
            fries = 1.89;
            drinks = 0.99;

            subtotal = Double.parseDouble (burgerInput.getText ()) * burgers 
                    + Double.parseDouble (fryInput.getText ()) * fries 
                    + Double.parseDouble (drinkInput.getText ()) * drinks;

            DecimalFormat w = new DecimalFormat("###,###0.00");
            subtotalOutput.setText("$" + w.format(subtotal));

    // Calculating Tax
            double taxpercentage;
            double tax;

            taxpercentage = 0.13;

            tax = subtotal * taxpercentage;

            DecimalFormat x = new DecimalFormat("###,###0.00");
            taxesOutput.setText("$" + x.format(tax));

    // Grand Total
            double grandtotal;

            grandtotal = subtotal + tax;

            DecimalFormat y = new DecimalFormat("###,###0.00");
            grandtotalOutput.setText("$" + y.format(grandtotal));

为了计算变化：

// Calculating Change
        double tendered;
        double grandtotal;
        double change;

        tendered = Double.parseDouble(tenderedInput.getText ());
        grandtotal = Double.parseDouble(grandtotalOutput.getText ());
        change = tendered - grandtotal;

        DecimalFormat z = new DecimalFormat("###,###0.00");
        changeOutput.setText("$" + z.format(change));

如果您能帮助我忽略“$”符号，让我在grandtotaloutput框中保留“$”，但仍然能够正确计算更改，我将不胜感激。谢谢！