gui JLIst runtime error - user-interface

Question

How do I fix my RemoveAction class so I don't get the following runtime error
Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: -1
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import java.util.List;
import java.util.ArrayList;
import java.io.*;
public class GuiDriver extends JFrame{
JList channelTitleJList, itemTitleJList;
DefaultListModel cModel, iModel;
List<RssReader> feedList = new ArrayList<RssReader>();
int nextFeed=0;
ListSelectionModel lsm;
public void addFeed(RssReader feed){
feedList.add(feed);
}
public JToolBar createToolBar(){
JToolBar bar = new JToolBar();
Action newToolBarButton = new AddAction("New");
Action deleteToolBarButton = new RemoveAction("Delete");
Action clearToolBarButton = new ClearAction("Clear");
bar.add(newToolBarButton);
bar.add(deleteToolBarButton);
bar.add(clearToolBarButton);
bar.setFloatable(false);
return bar;
}
public JSplitPane createJSplitPane(){
JSplitPane hSplitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,createChannelJScrollPane(), createItemJScrollPane());
hSplitPane.setDividerLocation(150);
return hSplitPane;
}
public JScrollPane createChannelJScrollPane(){
cModel = new DefaultListModel();
channelTitleJList = new JList(cModel);
JScrollPane channelJScrollPane = new JScrollPane(channelTitleJList);
channelTitleJList.setVisibleRowCount(20);
lsm = channelTitleJList.getSelectionModel();
lsm.addListSelectionListener(new ChannelListListener());
return channelJScrollPane;
}
public JScrollPane createItemJScrollPane(){
iModel = new DefaultListModel();
itemTitleJList = new JList(iModel);
JScrollPane itemJScrollPane = new JScrollPane(itemTitleJList);
//itemTitleJList.addListSelectionListener(new ItemListListener());
return itemJScrollPane;
}
public class AddAction extends AbstractAction{
public AddAction(String name){
super(name);
}
public void actionPerformed(ActionEvent e){
System.out.println(getValue(Action.NAME)+" selected.");
JOptionPane message = new JOptionPane();
String firstInput = message.showInputDialog(null, "Enter URL");
try{
DumpStockPage.readXml(firstInput);
File f = new File("RSSFeed.xml");
addFeed(new RssReader(f));
cModel.addElement(feedList.get(nextFeed).rssChannel.getTitle());
nextFeed++;
iModel.clear();
}
catch (IOException ee){
System.err.println(ee);
}
}
}
public class RemoveAction extends AbstractAction{
public RemoveAction(String name){
super(name);
}
public void actionPerformed(ActionEvent e){
cModel.removeElement(channelTitleJList.getSelectedValue());
iModel.clear();
}
}
public class ClearAction extends AbstractAction{
public ClearAction(String name){
super(name);
}
public void actionPerformed(ActionEvent e){
iModel.clear();
}
}
private class ChannelListListener implements ListSelectionListener{
public void valueChanged (ListSelectionEvent e) {
boolean adjust = e.getValueIsAdjusting();
if (!adjust) {
iModel.clear();
List<String> titles = new ArrayList<String>();
int i = channelTitleJList.getSelectedIndex(); //the index of the selected item in the left list
for(RssItem feed: feedList.get(i).rssChannel.items) {
iModel.addElement(feed.getTitle()); //build a list of titles, to be shown in the right list
}
}
}
}
/*
private class ItemListListener implements ListSelectionListener {
public void valueChanged (ListSelectionEvent e) {
boolean adjust = e.getValueIsAdjusting();
if (!adjust) {
int i = e.getLastIndex();
try{
JFrame w = new JFrame();
w.setTitle("Html Display");
w.setSize(1000, 600);
w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
w.setVisible(true);
JEditorPane htmlPane = new JEditorPane();
htmlPane.setPage(feedList.get(i).rssChannel.items.get(i).getLink());
w.add(new JScrollPane(htmlPane));
}
catch(Exception ee){
ee.printStackTrace();
}
}
}
}
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
GuiDriver frame = new GuiDriver();
frame.setTitle("RSS Reader");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(frame.createJSplitPane(), BorderLayout.NORTH);
frame.add(frame.createToolBar(), BorderLayout.SOUTH);
frame.setVisible(true);
frame.setSize(800,400);
}
});
}
}

Answer 1

add check to your ChannelListListener.valueChanged():
if (i==-1) return;
just before the for loop, or even better:
if (channelTitleJList.isSelectionEmpty()) return;