如果用户没有输入任何内容,如何验证整数字段？

Question

do{
         try{
            input = (String) JOptionPane.showInputDialog(null,"Food quantity","Dope Alley",JOptionPane.QUESTION_MESSAGE);
            quantity = Integer.parseInt(input);
            if(quantity <= 0 || quantity > 100){
                JOptionPane.showMessageDialog(null,"Invalid input . Number only .\n\nMininum order = 1\nMaximum order = 100","Dope Alley",JOptionPane.ERROR_MESSAGE);
            }
        }catch(NumberFormatException e){
            JOptionPane.showMessageDialog(null,"Invalid input . Number only .\n\nMininum order = 1\nMaximum order = 100","Dope Alley",JOptionPane.ERROR_MESSAGE);
        }
    }while(quantity <= 0 || quantity > 100);

catch(NumberFormatException e)如何在我的代码中澄清变量e？在我的代码中,程序声明不使用变量e.那我该怎么用呢

Answer 1

您可以使用正则表达式.\\d+将匹配连续数字.另外,我建议一个do-while循环.就像是

int quantity = -1;
do {
    input = (String) JOptionPane.showInputDialog(null, "Food quantity",
            "Dope Alley", JOptionPane.QUESTION_MESSAGE);
    if (input.matches("\\d+")) {
        quantity = Integer.parseInt(input);
    }
} while(quantity < 1 || quantity > 100);