Question

我正在尝试编写验证提款金额的代码。例如，如果提款金额大于余额，则应出现错误并说“无效提款金额”，但问题是当我输入无效金额时，会弹出错误消息。我尝试输入有效金额，它不会接受任何东西！它甚至不会让我关闭对话框。我该如何解决这个问题？

if (transactionChar== 'W' || transactionChar == 'w')
    {
      input = JOptionPane.showInputDialog("Please enter withdrawal amount."); 
      transactionAmount = Double.parseDouble(input); 
     while(transactionAmount >= oldBalance)
      input = JOptionPane.showInputDialog("Invalid withdrawal amount. Please enter valid withdrawal amount!");

  transactionAmount = Double.parseDouble(input); 

  newBalance = oldBalance - transactionAmount;

}

我的声明是

double oldBalance= 0;            //Holds the value of the old balance
String transactionType= "";      //Holds the value of the transaction type.
char transactionChar ;           //Gets input for either withdrawal or deposit
double transactionAmount= 0;

Answer 1

 while(transactionAmount >= oldBalance)
      input = JOptionPane.showInputDialog("Invalid withdrawal amount. Please enter valid withdrawal amount!");

您永远不会根据输入更新transactionAmount，因此while循环永远不会停止

试试这个

while(transactionAmount >= oldBalance) {
      input = JOptionPane.showInputDialog("Invalid withdrawal amount. Please enter valid withdrawal amount!");
      transactionAmount = Double.parseDouble(input);
}

您应该注意的其他几件事情：

如果我的帐户中有$ 100.00（oldBalance = 100.0）并且我尝试从我的帐户中提取100.00（transactionAmount == oldBalance），那么您的代码不允许我这样做。你不要让我把我的账户归零！

此外，似乎你要让我撤回负数。那是我的退步!! ：d

Answer 2

尝试使用

while(condition) 
{
   statement1;
   statement2;
}

而不是

while(condition)
statement1;
statement2;

Answer 3

如果您没有正确格式化代码，很难回答，但我认为您的代码是这样的：

if (transactionChar== 'W' || transactionChar == 'w') { 
    input = JOptionPane.showInputDialog("Please enter withdrawal amount.");
    transactionAmount = Double.parseDouble(input);
    while(transactionAmount >= oldBalance) 
        input = JOptionPane.showInputDialog("Invalid withdrawal amount. Please enter valid withdrawal amount!");

    transactionAmount = Double.parseDouble(input);
    newBalance = oldBalance - transactionAmount;
}

问题是您需要一个块{}来包含交易金额分配：

if (transactionChar== 'W' || transactionChar == 'w') { 
    input = JOptionPane.showInputDialog("Please enter withdrawal amount.");
    transactionAmount = Double.parseDouble(input);
    while(transactionAmount >= oldBalance) {
        input = JOptionPane.showInputDialog("Invalid withdrawal amount. Please enter valid withdrawal amount!");

            transactionAmount = Double.parseDouble(input);
    }
    newBalance = oldBalance - transactionAmount;
}

试图验证输入的问题

3 个答案: