如何解决数字格式异常:空字符串 [英] How to fix Number Format Exception: empty String

问题描述

在我的项目中，我要放置一个JTextField以在发票中设置总计.名称为txtGtotal.当客户支付预付款时，他在txtAdvance JTextField中键入其值，然后我在txtAdvance的密钥释放中写了一条代码，以将应付款项设置为txtDue JTextField. (如果客户不支付任何预付款，则应在txtAdvance中输入0，并且txtDue也应设置为0)

In my project I'm putting a JTextField to set grand total in the invoice. Its name is txtGtotal. When the customer pays an advance he type its value in txtAdvance JTextField, and I wrote a cord to txtAdvance's keyreleasing to set the due payment to txtDue JTextField. (If customer didn't pay any advance he should type as 0 in txtAdvance and txtDue also set 0)

下面是我关键活动的线索.

Given below is my cord to key event.

private void txtAdvanceKeyReleased(java.awt.event.KeyEvent evt) {
    double gtotal = Double.parseDouble(txtGtotal.getText());
    double ad = Double.parseDouble(txtAdvance.getText());
    double due = gtotal - ad;
}

我的问题是，当我清除txtAdvance中的数字值并尝试在键入之前键入另一个数字值时，得到此java.lang.NumberFormatException:空字符串错误.但是在我用数字值替换了空的txtAdvance jtextfeild之后，系统的措词正确.如何停止该错误.由于它们显示错误，所以在电线的第二行.会产生一个称为double ad的变量.

My question is when I'm clearing the number value in txtAdvance and try to type another number value before typing I'm getting this java.lang.NumberFormatException: empty String error. But after I replaced that empty txtAdvance jtextfeild with a number value, system is wording properly. How can I stop that error. As they showing error is in second line of the cord. which make a variable called double ad.

推荐答案

明显的解决方案如何:

private void txtAdvanceKeyReleased(java.awt.event.KeyEvent evt) {
    double gtotal = parseDouble(txtGtotal.getText());
    double ad = parseDouble(txtAdvance.getText());
    double due = gtotal - ad;
}

private double parseDouble(String s){
    if(s == null || s.isEmpty()) 
        return 0.0;
    else
        return Double.parseDouble(s);
}

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