"cannot be resolved"的问题,急急急

[charlesxu]

我下载了一段程序有三个类MailClient,Envelope,SMTPConnection(Envelope)，在MailClient里
生成了一个新的Envelope和SMTPConnection. 运行后报错(envelope cannot be resolved)，请问是什末原因？是不是需要在MailClient里引用Envelope呢?



public class MailClient{
try {
Envelope envelope = new Envelope(mailMessage,
serverField.getText());
} catch (UnknownHostException e) {
/* If there is an error, do not go further */
return;
}
try {
SMTPConnection connection = new SMTPConnection(envelope);
connection.send(envelope);
connection.close();
} catch (IOException error) {
System.out.println("Sending failed: " + error);
return;
}
}

public class Envelope
{}

public SMTPConnection(Envelope envelope)
{}

[charlesxu]

dingdingding

[charlesxu]

envelope这个类好像不被MailClient识别，帮帮我吧

[charlesxu]

这个是原程序，红色部分是出错的地方，报envelop cannot be resovled

package mailserver;

import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;

/* $Id: MailClient.java,v 1.7 1999/07/22 12:07:30 kangasha Exp $ */

/**
* A simple mail client with a GUI for sending mail.
*
* @author Jussi Kangasharju
*/
public class MailClient extends Frame {
/* The stuff for the GUI. */
private Button btSend = new Button("Send");
private Button btClear = new Button("Clear");
private Button btQuit = new Button("Quit");
private Label serverLabel = new Label("Local mailserver:");
private TextField serverField = new TextField("", 40);
private Label fromLabel = new Label("From:");
private TextField fromField = new TextField("", 40);
private Label toLabel = new Label("To:");
private TextField toField = new TextField("", 40);
private Label subjectLabel = new Label("Subject:");
private TextField subjectField = new TextField("", 40);
private Label messageLabel = new Label("Message:");
private TextArea messageText = new TextArea(10, 40);

/**
* Create a new MailClient window with fields for entering all
* the relevant information (From, To, Subject, and message).
*/
public MailClient() {
super("Java Mailclient");

/* Create panels for holding the fields. To make it look nice,
create an extra panel for holding all the child panels. */
Panel serverPanel = new Panel(new BorderLayout());
Panel fromPanel = new Panel(new BorderLayout());
Panel toPanel = new Panel(new BorderLayout());
Panel subjectPanel = new Panel(new BorderLayout());
Panel messagePanel = new Panel(new BorderLayout());
serverPanel.add(serverLabel, BorderLayout.WEST);
serverPanel.add(serverField, BorderLayout.CENTER);
fromPanel.add(fromLabel, BorderLayout.WEST);
fromPanel.add(fromField, BorderLayout.CENTER);
toPanel.add(toLabel, BorderLayout.WEST);
toPanel.add(toField, BorderLayout.CENTER);
subjectPanel.add(subjectLabel, BorderLayout.WEST);
subjectPanel.add(subjectField, BorderLayout.CENTER);
messagePanel.add(messageLabel, BorderLayout.NORTH);
messagePanel.add(messageText, BorderLayout.CENTER);
Panel fieldPanel = new Panel(new GridLayout(0, 1));
fieldPanel.add(serverPanel);
fieldPanel.add(fromPanel);
fieldPanel.add(toPanel);
fieldPanel.add(subjectPanel);

/* Create a panel for the buttons and add listeners to the
buttons. */
Panel buttonPanel = new Panel(new GridLayout(1, 0));
btSend.addActionListener(new SendListener());
btClear.addActionListener(new ClearListener());
btQuit.addActionListener(new QuitListener());
buttonPanel.add(btSend);
buttonPanel.add(btClear);
buttonPanel.add(btQuit);

/* Add, pack, and show. */
add(fieldPanel, BorderLayout.NORTH);
add(messagePanel, BorderLayout.CENTER);
add(buttonPanel, BorderLayout.SOUTH);
pack();
show();
}

static public void main(String argv[]) {
new MailClient();
}

/* Handler for the Send-button. */
class SendListener implements ActionListener {
public void actionPerformed(ActionEvent event) {
System.out.println("Sending mail");

/* Check that we have the local mailserver */
if ((serverField.getText()).equals("")) {
System.out.println("Need name of local mailserver!");
return;
}

/* Check that we have the sender and recipient. */
if((fromField.getText()).equals("")) {
System.out.println("Need sender!");
return;
}
if((toField.getText()).equals("")) {
System.out.println("Need recipient!");
return;
}

/* Create the message */
Message mailMessage = new Message(fromField.getText(),
toField.getText(),
subjectField.getText(),
messageText.getText());

/* Check that the message is valid, i.e., sender and
recipient addresses look ok. */
if(!mailMessage.isValid()) {
return;
}

/* Create the envelope, open the connection and try to send
the message. */
try {
Envelope envelope = new Envelope(mailMessage,
serverField.getText());
} catch (UnknownHostException e) {
/* If there is an error, do not go further */
return;
}
try {
SMTPConnection connection = new SMTPConnection(envelope);
connection.send(envelope); connection.close();
} catch (IOException error) {
System.out.println("Sending failed: " + error);
return;
}
System.out.println("Mail sent succesfully!");
}
}

/* Clear the fields on the GUI. */
class ClearListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.out.println("Clearing fields");
fromField.setText("");
toField.setText("");
subjectField.setText("");
messageText.setText("");
}
}

/* Quit. */
class QuitListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
}