Need help with java browser "Back" button

Question

All:
I'm trying to make the "Back" button in my Java web browser work. Any help would be greatly appreciated. Here is my code:
import javax.swing.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import java.util.*;
import java.io.*;
import javax.swing.text.html.*;
import javax.swing.text.*;
public class Browser implements HyperlinkListener, ActionListener
String source = "http://www.google.com";
final String GO = "Go";
final String Back = "Back";
JEditorPane ep = new JEditorPane(); //a JEditorPane allows display of HTML & RTF
JToolBar tb = new JToolBar(); //a JToolBar sits above the JEditorPane & contains
JTextField tf = new JTextField(40); // the JTextField & go button
JLabel address = new JLabel(" Address: ");
JButton back = new JButton(Back);
JButton go = new JButton(GO);
BorderLayout bl = new BorderLayout();
JPanel panel = new JPanel(bl);
JFrame frame = new JFrame("Billy Wolfe's Browser");
protected Vector history;
public Browser()
openURL(source); //this method (defined below) opens a page with address source
ep.setEditable(false); //this makes the HTML viewable only in teh JEditorPane, ep
ep.addHyperlinkListener(this); //this adds a listener for clicking on links
JScrollPane scroll = new JScrollPane(ep); //this puts the ep inside a scroll pane
panel.add(scroll,BorderLayout.CENTER); //adds the scroll pane to center of panel
tf.setActionCommand(GO); //gives the ActionListener on tf a name for its ActionEvent
tf.setActionCommand(Back);
tf.addActionListener(this); //adds an ActionListener to the JTextField (so user can
go.addActionListener(this); //use "Enter Key")
tb.add(back); //this adds the back button to the JToolBar
tb.add(address); //this adds the Label "Address:" to the JToolBar
tb.add(tf); //this adds the JTextField to the JToolBar
tb.add(go); //this adds the go button to the JToolBar
panel.add(tb,BorderLayout.NORTH); //adds the JToolBar to the top (North) of panel
frame.setContentPane(panel);
frame.setSize(1000,900);
frame.setVisible(true);
}// end Browser()
public void openURL(String urlString)
String start = urlString.substring(0,4);
if(!start.equals("http")) //adds "http://" to the URL if needed
urlString = "http://"+urlString;
}//end if
try
URL url = new URL(urlString);
ep.setPage(url); //this sets the ep page to the URL page
tf.setText(urlString); //this sets the JTextField, tf, to the URL
catch (Exception e)
{ System.out.println("Can't open "+source+" "+e);
}//end try-catch
}//end openURL
public void hyperlinkUpdate(HyperlinkEvent he) //this allows linking
HyperlinkEvent.EventType type = he.getEventType();
if(type == HyperlinkEvent.EventType.ACTIVATED)
openURL(he.getURL().toExternalForm());
history.add(he.getURL().toExternalForm());
}//end hyperlinkUpdate()
public void actionPerformed(ActionEvent ae) //for the GO and BACK buttons
String command = ae.getActionCommand();
if(command.equals(GO))
openURL(tf.getText());
history.add(tf.getText());
//JOptionPane.showMessageDialog(null, "This is a test");
if(command.equals(Back))
try
String lastURL = (String)history.lastElement();
history.removeElement(lastURL);
lastURL = (String)history.lastElement();
// JOptionPane.showMessageDialog(null, lastURL);
ep.setPage(lastURL);
if (history.size() == 1)
back.setEnabled(false);
catch (Exception e)
System.out.println("ERROR: Trouble fetching URL");}
}//end actionPerformed()
}// end Browser class

Answer 1

Here it is. I need to be able to click the Back button and view the previous URL.
import javax.swing.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import java.util.*;
import java.io.*;
import javax.swing.text.html.*;
import javax.swing.text.*;
public class Browser implements HyperlinkListener, ActionListener
String source = "http://www.google.com";
final String GO = "Go";
final String Back = "Back";
JEditorPane ep = new JEditorPane(); //a JEditorPane allows display of HTML & RTF
JToolBar tb = new JToolBar(); //a JToolBar sits above the JEditorPane & contains
JTextField tf = new JTextField(40); // the JTextField & go button
JLabel address = new JLabel(" Address: ");
JButton back = new JButton(Back);
JButton go = new JButton(GO);
BorderLayout bl = new BorderLayout();
JPanel panel = new JPanel(bl);
JFrame frame = new JFrame("Billy Wolfe's Browser");
protected Vector history;
public Browser()
openURL(source); //this method (defined below) opens a page with address source
ep.setEditable(false); //this makes the HTML viewable only in teh JEditorPane, ep
ep.addHyperlinkListener(this); //this adds a listener for clicking on links
JScrollPane scroll = new JScrollPane(ep); //this puts the ep inside a scroll pane
panel.add(scroll,BorderLayout.CENTER); //adds the scroll pane to center of panel
tf.setActionCommand(GO); //gives the ActionListener on tf a name for its ActionEvent
tf.setActionCommand(Back);
tf.addActionListener(this); //adds an ActionListener to the JTextField (so user can
go.addActionListener(this); //use "Enter Key")
tb.add(back); //this adds the back button to the JToolBar
tb.add(address); //this adds the Label "Address:" to the JToolBar
tb.add(tf); //this adds the JTextField to the JToolBar
tb.add(go); //this adds the go button to the JToolBar
panel.add(tb,BorderLayout.NORTH); //adds the JToolBar to the top (North) of panel
frame.setContentPane(panel);
frame.setSize(1000,900);
frame.setVisible(true);
}// end Browser()
public void openURL(String urlString)
String start = urlString.substring(0,4);
if(!start.equals("http")) //adds "http://" to the URL if needed
urlString = "http://"+urlString;
}//end if
try
URL url = new URL(urlString);
ep.setPage(url); //this sets the ep page to the URL page
tf.setText(urlString); //this sets the JTextField, tf, to the URL
catch (Exception e)
{ System.out.println("Can't open "+source+" "+e);
}//end try-catch
}//end openURL
public void hyperlinkUpdate(HyperlinkEvent he) //this allows linking
HyperlinkEvent.EventType type = he.getEventType();
if(type == HyperlinkEvent.EventType.ACTIVATED)
openURL(he.getURL().toExternalForm());
history.add(he.getURL().toExternalForm());
}//end hyperlinkUpdate()
public void actionPerformed(ActionEvent ae) //for the GO and BACK buttons
String command = ae.getActionCommand();
if(command.equals(GO))
openURL(tf.getText());
history.add(tf.getText());
//JOptionPane.showMessageDialog(null, "This is a test");
if(command.equals(Back))
try
String lastURL = (String)history.lastElement();
history.removeElement(lastURL);
lastURL = (String)history.lastElement();
// JOptionPane.showMessageDialog(null, lastURL);
ep.setPage(lastURL);
if (history.size() == 1)
back.setEnabled(false);
catch (Exception e)
System.out.println("ERROR: Trouble fetching URL");}
}//end actionPerformed()
}// end Browser class