java - JTextField只显示绝对值，没有负号？

Question

我正在开发一个“银行帐户”类型的程序，我的目标是取款和存钱，显示更新的余额，显示帐户状态( overdraw 与否)。我刚刚得到了添加/减去和更新平衡工作，但是我的 JTextFields 中的数字是绝对值，并且不显示负余额(余额 < 0)。我需要做某种格式吗？我已经包含了按钮监听器的代码以及我所做的一些解析将 double 转换为字符串等。请帮忙!

     depositButton.addActionListener(new DepositListener());
     withdrawButton.addActionListener(new WithdrawListener());

    //create object of BankAccount, assign values to the text fields
     BankAccount myAcct = new BankAccount(1524687, 100.00, "Landon Wiggs");
     acctNameF.setText(myAcct.getName() );
     acctNumF.setText(Integer.toString( myAcct.getAcctNumber() ) );
     acctBalanceF.setText( Double.toString(myAcct.getBalance()));
     depositWithdrawAmtF.setText("0.00");


  private class DepositListener implements ActionListener 
{
      public void actionPerformed (ActionEvent event)
      {  
         double sum = Double.valueOf(depositWithdrawAmtF.getText()) + Double.valueOf(acctBalanceF.getText());
         double amt = (Double.parseDouble(depositWithdrawAmtF.getText()));
         acctBalanceF.setText(Double.toString(sum)); 
      }
   }

private class WithdrawListener implements ActionListener {
      public void actionPerformed (ActionEvent event) {
         double sum = (Double.valueOf(depositWithdrawAmtF.getText() )) - (Double.valueOf(acctBalanceF.getText() ));
         double amt = (Double.parseDouble(depositWithdrawAmtF.getText()));

         acctBalanceF.setText(Double.toString(sum));   
      }
   }

Answer 1

当您提款时，您可能应该从账户资金中减去提款金额，现在您正在做相反的事情。

改变

double sum = (Double.valueOf(depositWithdrawAmtF.getText() )) - (Double.valueOf(acctBalanceF.getText() ));

至

double sum = Double.valueOf(acctBalanceF.getText()) - Double.valueOf(depositWithdrawAmtF.getText());