这是针对我作为家庭作业的一部分正在编写的 Java 程序。我不想为我完成工作，但我被困住了。我对 Java 还很陌生，并且使用的是 NetBeans IDE 7.0.1。
在尝试验证用户输入时，我在处理一些异常时遇到了困难。该程序将根据用户输入记录慈善捐赠。但是，我没有成功验证捐赠金额文本字段输入。如果用户输入文本而不是数字，我希望他们被通知他们的输入无效，并且我希望异常处理来处理错误并在用户修复他们的输入后继续。任何帮助是极大的赞赏。
这是我的代码：
package donorgui;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.io.*;
import java.awt.*;
public class DonorGUI extends JFrame
{
// Components
private JPanel panel;
private JTextArea results;
private JButton entryButton;
private JButton exitButton;
private JButton clearButton;
private JTextField donorField;
private JTextField charityField;
private JTextField pledgeField;
//create variables
String[] donorName = new String[20];
String[] charityName = new String[20];
double[] donationAmt = new double[20];
int i = 0;
// Constants for the window size
private final int WINDOW_WIDTH = 750;
private final int WINDOW_HEIGHT = 510;
//Constructor
public DonorGUI(){
// Set the title.
setTitle("Donor");
// Specify what happens when the close button is clicked.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Build the panel that contains the other components.
buildPanel();
// Add the panel to the content pane.
add(panel);
// Size and display the window.
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
setVisible(true);
}
//The buildPanel method creates a panel containing other components.
private void buildPanel(){
// Create labels to display instructions.
JLabel message1 = new JLabel("Name of the Donor:");
JLabel message2 = new JLabel("Name of the Charity:");
JLabel message3 = new JLabel("Amount of the Pledge:");
//instantiate the results area
results = new JTextArea(25,60);
// Create text fields to receive user input
donorField = new JTextField(10);
charityField = new JTextField(10);
pledgeField = new JTextField(10);
//create the user buttons to cause action
entryButton = new JButton("Enter Donation.");
entryButton.addActionListener(new EntryButtonListener());
exitButton = new JButton("EXIT");
exitButton.addActionListener(new ExitButtonListener());
clearButton = new JButton ("Clear Fields");
clearButton.addActionListener(new ClearButtonListener());
// Create a panel.
panel = new JPanel();
//set the LayoutManager
panel.setLayout(new FlowLayout());
// Add the labels, text fields, and button to the panel.
panel.add(message1);
panel.add(donorField);
panel.add(message2);
panel.add(charityField);
panel.add(message3);
panel.add(pledgeField);
panel.add(results);
panel.add(entryButton);
panel.add(exitButton);
panel.add(clearButton);
}
private class EntryButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
donorName[i] = donorField.getText();
charityName[i] = charityField.getText();
donationAmt[i] = Double.parseDouble(pledgeField.getText());
results.append(donorName[i]+" "+charityName[i]+" "+donationAmt[i]+"\n ");
i++;
}
}
public boolean donationAmt(String amount) {
int i = 0;
try {
i = Integer.parseInt (amount);
return true;
}
catch (NumberFormatException e) {
JOptionPane.showMessageDialog(null, "Invalid Input. Please enter a dollar amount");
return false;
}
}
private class ClearButtonListener implements ActionListener {
@Override
public void actionPerformed (ActionEvent e) {
donorField.setText("");
charityField.setText("");
pledgeField.setText("");
}
}
private class ExitButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
/* Application method */
public static void main(String[] args){
DonorGUI rpc = new DonorGUI();
}
}
这是我修改后的代码。经过一些用户输入测试后，当我使用 100.00、40.00 等...而不是整美元金额（例如 100、40 等）时出现异常。有什么想法吗？
package donorgui;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.io.*;
import java.awt.*;
public class DonorGUI extends JFrame
{
// Components
private JPanel panel;
private JTextArea results;
private JButton entryButton;
private JButton exitButton;
private JButton clearButton;
private JTextField donorField;
private JTextField charityField;
private JTextField pledgeField;
//create variables
String[] donorName = new String[20];
String[] charityName = new String[20];
double[] donationAmt = new double[20];
int i = 0;
// Constants for the window size
private final int WINDOW_WIDTH = 750;
private final int WINDOW_HEIGHT = 550;
//Constructor
public DonorGUI(){
// Set the title.
setTitle("Donor");
// Specify what happens when the close button is clicked.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Build the panel that contains the other components.
buildPanel();
// Add the panel to the content pane.
add(panel);
// Size and display the window.
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
setVisible(true);
}
//The buildPanel method creates a panel containing other components.
private void buildPanel(){
// Create labels to display instructions.
JLabel message1 = new JLabel("Name of the Donor:");
JLabel message2 = new JLabel("Name of the Charity:");
JLabel message3 = new JLabel("Amount of the Pledge:");
//instantiate the results area
results = new JTextArea(25,60);
// Create text fields to receive user input
donorField = new JTextField(10);
charityField = new JTextField(10);
pledgeField = new JTextField(10);
//create the user buttons to cause action
entryButton = new JButton("Enter Donation.");
entryButton.addActionListener(new EntryButtonListener());
exitButton = new JButton("EXIT");
exitButton.addActionListener(new ExitButtonListener());
clearButton = new JButton ("Clear Fields");
clearButton.addActionListener(new ClearButtonListener());
// Create a panel.
panel = new JPanel();
//set the LayoutManager
panel.setLayout(new FlowLayout());
// Add the labels, text fields, and button to the panel.
panel.add(message1);
panel.add(donorField);
panel.add(message2);
panel.add(charityField);
panel.add(message3);
panel.add(pledgeField);
panel.add(results);
panel.add(entryButton);
panel.add(exitButton);
panel.add(clearButton);
}
private class EntryButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
donorName[i] = donorField.getText();
charityName[i] = charityField.getText();
if (donationAmt(pledgeField.getText())) {
donationAmt[i] = Double.parseDouble(pledgeField.getText());
}
results.append(donorName[i]+" "+charityName[i]+" "+donationAmt[i]+"\n ");
i++;
}
}
public boolean donationAmt(String amount) {
if(amount==null || amount=="" || amount.length()<1){ //checking for empty field
JOptionPane.showMessageDialog(null, "Please enter a dollar amount");
return false;
}
for(int i = 0; i < amount.length(); i++){ //verifying dollar amount entered as number
if (!Character.isDigit(amount.charAt(i))){
JOptionPane.showMessageDialog(null, "Invalid input. Please enter a dollar amount");
return false;
}
}
return true;
}
private class ClearButtonListener implements ActionListener {
@Override
public void actionPerformed (ActionEvent e) {
donorField.setText("");
charityField.setText("");
pledgeField.setText("");
}
}
private class ExitButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
/* Application method */
public static void main(String[] args){
DonorGUI rpc = new DonorGUI();
}
}