Convert the following program so that it uses JList instead of JComboBox. import
ID: 3939667 • Letter: C
Question
Convert the following program so that it uses JList instead of JComboBox.
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.List;
import javax.swing.*;
public class ShoppingList extends JFrame {
private static final long myShoppingList = 1L;
// Constants for window width and height
private final int WINDOW_WIDTH = 700;
private final int WINDOW_HEIGHT = 250;
private JTextField shoppingList;
// Buttons for Save, Add, Remove, and Load features.
private JButton Save;
private JButton Add;
private JButton Remove;
private JButton Load;
// Panels for the button groups
private JPanel textfieldPanel;
private JPanel buttonPanel;
private JComboBox<String> itemList;
/**
* CONSTRUCTOR
*/
public ShoppingList() {
// Window title
setTitle("Shopping List");
// Set size
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
// Default close operation
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Calling buildPanel method
buildPanels();
// Grid Layout
setLayout(new FlowLayout());
// Adding the panel to JFrame
add(textfieldPanel);
add(buttonPanel);
// Visibility
setVisible(true);
}
// Building the Panels,
private void buildPanels() {
// Initializing the Textfield
shoppingList = new JTextField(20);
// Initializing the Buttons
Save = new JButton("Save");
Add = new JButton("Add");
Remove = new JButton("Remove");
Load = new JButton("Load");
// Associating action listener
Add.addActionListener(new AddButtonListener());
Save.addActionListener(new SaveButtonListener());
Remove.addActionListener(new RemoveButtonListener());
Load.addActionListener(new LoadButtonListener());
try {
itemList = new JComboBox<>(fileToArray());
} catch (IOException e) {
itemList = new JComboBox<>();
}
itemList.setPreferredSize(new Dimension(10,20));
// Initializing the panels
textfieldPanel = new JPanel();
buttonPanel = new JPanel();
// Seting borders of the panels
textfieldPanel.setBorder(BorderFactory
.createTitledBorder("Shopping List"));
buttonPanel.setBorder(BorderFactory.createTitledBorder("Process"));
// Adding the objecs to the respective panels
textfieldPanel.setLayout(new BoxLayout(textfieldPanel, BoxLayout.Y_AXIS));
textfieldPanel.add(shoppingList);
textfieldPanel.add(itemList);
buttonPanel.add(Save);
buttonPanel.add(Add);
buttonPanel.add(Remove);
buttonPanel.add(Load);
}// End buildPanels
private class AddButtonListener implements ActionListener {
public void actionPerformed(ActionEvent addaction) {
if (!shoppingList.getText().trim().equals(""))
itemList.addItem(shoppingList.getText().trim().toLowerCase());
}
}//end listener
private class RemoveButtonListener implements ActionListener {
public void actionPerformed(ActionEvent removeaction) {
if (itemList.getItemCount() > 0)
itemList.removeItemAt(itemList.getSelectedIndex());
else {
JOptionPane.showMessageDialog(null, "Please select an item to delete!");
}
}
}//end listener
private class SaveButtonListener implements ActionListener {
public void actionPerformed(ActionEvent saveaction) {
try {
writeToFile();
}
catch (Exception n) {
System.out.println("File not created!");
}
}
}//end listener
private void writeToFile() throws FileNotFoundException, IOException {
PrintWriter inFile = new PrintWriter(new File("list.txt"));
FileWriter writer = (new FileWriter("list.txt", true));
writer.write(shoppingList.getText().trim().toLowerCase());
writer.write(" ");
writer.close();
inFile.close();
}
private class LoadButtonListener implements ActionListener {
public void actionPerformed(ActionEvent loadaction) {
try {
for (String item : fileToArray()) {
itemList.addItem(item);
}
}
catch (Exception o)
{
JOptionPane.showMessageDialog(null, "Error opening data file");
}
}
}//end listener
private String[] fileToArray() throws IOException {
Path filePath = new File("list.txt").toPath();
Charset charset = Charset.defaultCharset();
List<String> stringList = Files.readAllLines(filePath, charset);
return stringList.toArray(new String[] {});
}
public static void main(String[] args) throws IOException {
new ShoppingList();
}
}// end main
Explanation / Answer
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ComboBoxTwo extends JPanel implements ActionListener
{
private JComboBox<String> mainComboBox;
private JComboBox<String> subComboBox;
private Hashtable<String, String[]> subItems = new Hashtable<String, String[]>();
public ComboBoxTwo()
{
String[] items = { "Select Item", "Color", "Shape", "Fruit" };
mainComboBox = new JComboBox<String>( items );
mainComboBox.addActionListener( this );
// prevent action events from being fired when the up/down arrow keys are used
mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
add( mainComboBox );
// Create sub combo box with multiple models
subComboBox = new JComboBox<String>();
subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
add( subComboBox );
String[] subItems1 = { "Select Color", "Red", "Blue", "Green" };
subItems.put(items[1], subItems1);
String[] subItems2 = { "Select Shape", "Circle", "Square", "Triangle" };
subItems.put(items[2], subItems2);
String[] subItems3 = { "Select Fruit", "Apple", "Orange", "Banana" };
subItems.put(items[3], subItems3);
}
public void actionPerformed(ActionEvent e)
{
String item = (String)mainComboBox.getSelectedItem();
Object o = subItems.get( item );
if (o == null)
{
subComboBox.setModel( new DefaultComboBoxModel() );
}
else
{
subComboBox.setModel( new DefaultComboBoxModel( (String[])o ) );
}
}
private static void createAndShowUI()
{
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( new ComboBoxTwo() );
frame.setLocationByPlatform( true );
frame.pack();
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}