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Question

我試圖將錯誤消息彈出說

Error: Amount is required

當他們在盒子還沒有添加量破例。以下是我有：

String output = "Gas Amount: $" + gasAmount + 
         "\nCar Wash: " + price; 
    try { 
     throw new AmountException(); 
    JOptionPane.showMessageDialog(null, output); 
    } 
    catch (AmountException ae) { 
    JOptionPane.showMessageDialog(null, ae.toString(), "Error", JOptionPane.ERROR_MESSAGE);  
    } 
     } 

Answer 1

事情是這樣的：

public class AmountException extends Throwable 
{ 
    public AmountException() 
    { 
    super("Error: Amount is required!!"); 
    } 
} 

在您的代碼：

try 
{ 
    if (gasAmount == null) 
    throw new AmountException(); 
    JOptionPane.showMessageDialog(null, output); 
} 
catch (AmountException ae) 
{ 
    JOptionPane.showMessageDialog(null, ae.getMessage(), "Error", JOptionPane.ERROR_MESSAGE); 
}