JList in java swings

hi usha

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class JListExample extends JPanel implements ListSelectionListener {
private JList list;
private DefaultListModel lm;

private static final String save = "Save";
private static final String del = "Delete";
private JButton jbutton;
private JTextField textfield;

public JListExample() {
super(new BorderLayout());

lm = new DefaultListModel();
lm.addElement("Amardeep");
lm.addElement("Deepak");
lm.addElement("Vinod");
lm.addElement("chandan");
lm.addElement("noor");
lm.addElement("vikash");
lm.addElement("suman");
lm.addElement("Neelam");
lm.addElement("soroj");

//Create the list and put it in a scroll pane.
list = new JList(lm);
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
list.setSelectedIndex(0);
list.addListSelectionListener(this);
list.setVisibleRowCount(5);
JScrollPane listScrollPane = new JScrollPane(list);

JButton sbutton = new JButton(save);
SaveListener slist = new SaveListener(sbutton);
sbutton.setActionCommand(save);
sbutton.addActionListener(slist);
sbutton.setEnabled(false);

jbutton = new JButton(del);
jbutton.setActionCommand(del);
jbutton.addActionListener(new DeleteListener());

textfield = new JTextField(10);
textfield.addActionListener(slist);
textfield.getDocument().addDocumentListener(slist);
String name = lm.getElementAt(list.getSelectedIndex()).toString();
//Create a panel that uses BoxLayout.
JPanel buttonPane = new JPanel();
buttonPane.setLayout(new BoxLayout(buttonPane, BoxLayout.LINE_AXIS));
buttonPane.add(jbutton);
buttonPane.add(Box.createHorizontalStrut(5));
buttonPane.add(new JSeparator(SwingConstants.VERTICAL));
buttonPane.add(Box.createHorizontalStrut(5));
buttonPane.add(textfield);
buttonPane.add(sbutton);
buttonPane.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
add(listScrollPane, BorderLayout.CENTER);
add(buttonPane, BorderLayout.PAGE_END);
}
class DeleteListener implements ActionListener {
public void actionPerformed(ActionEvent e){
int index = list.getSelectedIndex();
lm.remove(index);
int size = lm.getSize();
if (size == 0) { //Nobody's left, disable firing.
jbutton.setEnabled(false);

} else { //Select an index.
if (index == lm.getSize()) {
//removed item in last position
index--;
}
list.setSelectedIndex(index);
list.ensureIndexIsVisible(index);
}
}
}

//This listener is shared by the text field and the hire button.
class SaveListener implements ActionListener, DocumentListener {
private boolean alreadyEnabled = false;
private JButton button;
public SaveListener(JButton button){
this.button = button;
}
//Required by ActionListener.
public void actionPerformed(ActionEvent e) {
String name = textfield.getText();

//User didn't type in a unique name...
if (name.equals("") || alreadyInList(name)) {
Toolkit.getDefaultToolkit().beep();
textfield.requestFocusInWindow();
textfield.selectAll();
return;
}

int index = list.getSelectedIndex(); //get selected index
if (index == -1) { //no selection, so insert at beginning
index = 0;
} else { //add after the selected item
index++;
}

lm.insertElementAt(textfield.getText(), index);
//Reset the text field.
textfield.requestFocusInWindow();
textfield.setText("");
//Select the new item and make it visible.
list.setSelectedIndex(index);
list.ensureIndexIsVisible(index);
}
protected boolean alreadyInList(String name) {
return lm.contains(name);
}
//Required by DocumentListener.
public void insertUpdate(DocumentEvent e) {
enableButton();
}
//Required by DocumentListener.
public void removeUpdate(DocumentEvent e){
handleTextField(e);
}

//Required by DocumentListener.
public void changedUpdate(DocumentEvent e) {
if (!handleTextField(e)) {
enableButton();
}
}

private void enableButton() {
if (!alreadyEnabled) {
button.setEnabled(true);
}
}
private boolean handleTextField(DocumentEvent e) {
if (e.getDocument().getLength() <= 0) {
button.setEnabled(false);
alreadyEnabled = false;
return true;
}
return false;
}
}

//This method is required by ListSelectionListener.
public void valueChanged(ListSelectionEvent e) {
if (e.getValueIsAdjusting() == false) {

if (list.getSelectedIndex() == -1) {
//No selection, disable fire button.
jbutton.setEnabled(false);

} else {
//Selection, enable the fire button.
jbutton.setEnabled(true);
}
}
}
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("JList frame example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new JListExample();
newContentPane.setOpaque(true);
frame.setContentPane(newContentPane);
frame.setSize(300,300);
frame.setVisible(true);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable(){
public void run() {
createAndShowGUI();
}
});
}
}

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Thank.