我有这个学校的程序，当你填写所有文本字段时它工作正常。但是，如果在字段上留下任何空白，整个程序将崩溃。这是我的代码：
/** Kyle N Welch
* Sept 29th, 2017
* This program will calculate the expanses of a business
* man/woman on a business trip using the GUI
* */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
//Class name declaration
public class KNW_TravelExpenses extends JFrame
{
private JPanel travelInfoPanel;
private JPanel buttonPanel;
// Labels
private JLabel numDaysOnTripLabel;
private JLabel amountAirfairLabel;
private JLabel amountCarRentalLabel;
private JLabel milesDrivenLabel;
private JLabel parkingFeesLabel;
private JLabel taxiFeesLabel;
private JLabel confRegLabel;
private JLabel lodgingChargesPerNightLabel;
// Text Fields
private JTextField numDaysOnTripTextField;
private JTextField amountAirfairTextField;
private JTextField amountCarRentalTextField;
private JTextField milesDrivenTextField;
private JTextField parkingFeesTextField;
private JTextField taxiFeesTextField;
private JTextField confRegTextField;
private JTextField lodgingChargesPerNightTextField;
// Buttons
private JButton resetButton;
private JButton calcButton;
// Meals amount reimbursed by company per day.
private double mealsAmount = 37.00;
// Parking Fees amount reimbursed by company per day.
private double parkingFeesReimbursed = 10.00;
// Taxi Charges amount reimbursed by company per day.
private double taxiChargesReimbursed = 20.00;
// Lodging Charges amount reimbursed by company per day.
private double lodgingChargesReimbursed = 95.00;
// Private Vehicle per miles reimbursment rate.
private double prVechiclePerMileReimbursed = 0.27;
// Constructor
public KNW_TravelExpenses( )
{
//set the title.
super("TRAVEL EXPENSES");
// Set the main window
setLocationRelativeTo(null);
// Specify an action for the close button.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a BorderLayout manager for the content pane.
setLayout(new BorderLayout());
// Build the TravelInfo and Buttons panels
buildTravelInfoPanel();
buildButtonPanel();
// Add the panels to the frame's content pane
add(travelInfoPanel, BorderLayout.CENTER);
add(buttonPanel, BorderLayout.SOUTH);
// Pack the contents of the window and display it.
pack();
setVisible(true);
}
// The buildTravelInfoPanel method adds the labels
//and text fiels to the TravelInfo panel.
private void buildTravelInfoPanel()
{
// Create the labels for TravelInfo fields
numDaysOnTripLabel = new JLabel("Number of days on trip: ");
amountAirfairLabel = new JLabel("Amount of airfair: ");
amountCarRentalLabel = new JLabel("Amount of car rental fees: ");
milesDrivenLabel = new JLabel("Number of Miles driven: ");
parkingFeesLabel = new JLabel("Amount of Parking fees: ");
taxiFeesLabel = new JLabel("Amount of Tax charges: ");
confRegLabel = new JLabel("Conference or Seminar registration fees: ");
lodgingChargesPerNightLabel = new JLabel("Lodging charges per night: ");
// Create the text boxes for TravelInfo user input
numDaysOnTripTextField = new JTextField(3);
amountAirfairTextField = new JTextField(8);
amountCarRentalTextField = new JTextField(8);
milesDrivenTextField = new JTextField(4);
parkingFeesTextField = new JTextField(6);
taxiFeesTextField = new JTextField(6);
confRegTextField = new JTextField(8);
lodgingChargesPerNightTextField = new JTextField(6);
// Create a panel to hold labels and text fields.
travelInfoPanel = new JPanel();
// Create GridLayout manager
travelInfoPanel.setLayout(new GridLayout(10, 2));
// Add the labels and text fields to this panel.
travelInfoPanel.add(numDaysOnTripLabel);
travelInfoPanel.add(numDaysOnTripTextField);
travelInfoPanel.add(amountAirfairLabel);
travelInfoPanel.add(amountAirfairTextField);
travelInfoPanel.add(amountCarRentalLabel);
travelInfoPanel.add(amountCarRentalTextField);
travelInfoPanel.add(milesDrivenLabel);
travelInfoPanel.add(milesDrivenTextField);
travelInfoPanel.add(parkingFeesLabel);
travelInfoPanel.add(parkingFeesTextField);
travelInfoPanel.add(taxiFeesLabel);
travelInfoPanel.add(taxiFeesTextField);
travelInfoPanel.add(confRegLabel);
travelInfoPanel.add(confRegTextField);
travelInfoPanel.add(lodgingChargesPerNightLabel);
travelInfoPanel.add(lodgingChargesPerNightTextField);
// Add an empty border around the panel for spacing.
travelInfoPanel.setBorder(BorderFactory.createEmptyBorder(10, 10, 1, 10));
}
/*** The buildButtonPanel method creates and adds the Reset and Calculate
* buttons to the TravelExpense panel as its own panel.
*/
private void buildButtonPanel()
{
// Create the calcButton.
calcButton = new JButton("CALCULATE");
// Register an event listener
calcButton.addActionListener(new CalcButtonListener());
//Create the resetButton.
resetButton = new JButton("RESET");
// Create the Buttons panels.
buttonPanel = new JPanel();
buttonPanel.setLayout(new BorderLayout(5, 5));
buttonPanel.add(resetButton, BorderLayout.WEST);
buttonPanel.add(calcButton, BorderLayout.CENTER);
//Add an empty border around the panel for spacing.
buttonPanel.setBorder(BorderFactory.createEmptyBorder(1, 10, 10, 10));
}
/** Private inner class that handles the event when the user clicks
* the Calculate button .
*/
private class CalcButtonListener implements ActionListener
{
// Declare variables
String input;
int days;
double air;
double carRental;
double miles;
double parking;
double taxi;
double confReg;
double lodging;
double mealsAmount;
public void actionPerformed(ActionEvent e)
{
//Declare variables
double actualExpenses;
double milesExpenses;
double allowableExpenses;
double excessAir;
double excessCarRental;
double excessParking;
double excessTaxi;
double excessLodging;
double excessAmountTotal;
double amountSaved=0;
double paidBackAmount=0;
//Create a DecimalFormat object to format the totals as dollar amounts.
DecimalFormat dollar = new DecimalFormat("$#,##0.00");
//Get Input Data the user entered in the text fields.
days = Integer.parseInt(numDaysOnTripTextField.getText());
air = Double.parseDouble(amountAirfairTextField.getText());
carRental = Double.parseDouble(amountCarRentalTextField.getText());
miles = Double.parseDouble(milesDrivenTextField.getText());
parking = Double.parseDouble(parkingFeesTextField.getText());
taxi = Double.parseDouble(taxiFeesTextField.getText());
confReg = Double.parseDouble(confRegTextField.getText());
lodging = Double.parseDouble(lodgingChargesPerNightTextField.getText());
//Determine actualExpenses method.
milesExpenses = miles * prVechiclePerMileReimbursed;
actualExpenses = (carRental + parking + taxi + lodging +mealsAmount)
*days+air+milesExpenses+ confReg ;
// Calculate the allowableExpenses.
allowableExpenses=(mealsAmount+parkingFeesReimbursed+taxiChargesReimbursed+lodgingChargesReimbursed)
*days+milesExpenses+air+confReg;
// Calculate the paidBackAmount.
if(actualExpenses>allowableExpenses)
paidBackAmount=actualExpenses-allowableExpenses;
else
amountSaved=allowableExpenses-actualExpenses;
// Display the Totals message box.
if(paidBackAmount>0)
JOptionPane.showMessageDialog(null, "Total expenses: "
+ dollar.format(actualExpenses) +"\n" +"Allowable expenses: "
+ dollar.format(allowableExpenses)+"\n" +"\n" + "Amount to be paid back: "
+dollar.format(paidBackAmount));
else if(amountSaved>0)
JOptionPane.showMessageDialog(null, "Total expenses: " + dollar.format(actualExpenses)
+"\n" +"Allowable expenses: " + dollar.format(allowableExpenses)+"\n" +
"\n" + "Amount Saved: "+dollar.format(amountSaved));
else
JOptionPane.showMessageDialog(null, "Total expenses: " + dollar.format(actualExpenses)
+"\n" +"Allowable expenses: " + dollar.format(allowableExpenses)+"\n" );
}
}
/*** Private inner class that handles the event when the user clicks
* the RESET button .
*/
private class ResetButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
numDaysOnTripTextField.setText(" ");
amountAirfairTextField.setText(" ");
amountCarRentalTextField.setText(" ");
milesDrivenTextField.setText(" ");
parkingFeesTextField.setText(" ");
taxiFeesTextField.setText(" ");
confRegTextField.setText(" ");
lodgingChargesPerNightTextField.setText(" ");
}
}
// The main method
public static void main(String[] args)
{
new TravelExpenses();
}
}
当字段留空时可能导致GUI程序崩溃的任何内容。必须有一些东西，我显然错过了它。如果您可以向我指出并告诉我如何修复它，那么任何帮助都会受到赞赏吗？
答案 0 :(得分：1)
使用parseInt时尝试使用try-catch，因为它的加注FormatException（从parseInt字符串尝试null可以以崩溃结束。）
答案 1 :(得分：0)
最有可能的是，错误发生是因为您尝试将空字符串视为数字。该程序是否适用于缺少数据？如果是，您必须修改计算，将空白视为零或以其他方式处理。
重要的一课是查看堆栈跟踪。 Java会告诉你到底出错的地方和地点。正如其他人所说，要么将程序减少到最小程度，要么我们不必猜测，要么提供堆栈跟踪。