hi,
DefaultListModel listModel =3D new DefaultListModel(); // model for =
the JList
JList list =3D new JList(listModel);

you can add element at runtime using
listModel.addElement(Object obj); or
listmodel.add(int index, Object obj)
list gets updated once you add element..

i hope this will do..

Hi friend,


i am sending working code.

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


public class SingleList extends JPanel implements ListSelectionListener {
private JList list;
private DefaultListModel listModel;
private static final String saveString = "Save";
private static final String delString = "Delete";
private JButton deleteButton;
private JTextField ename;

public SingleList() {
super(new BorderLayout());
listModel = new DefaultListModel();
listModel.addElement("Amardeep");
listModel.addElement("Vinod");
listModel.addElement("Suman");

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

JButton hireButton = new JButton(saveString);
SaveListener save = new SaveListener(hireButton);
hireButton.setActionCommand(saveString);
hireButton.addActionListener(save);
hireButton.setEnabled(false);

deleteButton = new JButton(delString);
deleteButton.setActionCommand(delString);
deleteButton.addActionListener(new DeleteListener());

ename = new JTextField(10);
ename.addActionListener(save);
ename.getDocument().addDocumentListener(save);
String name = listModel.getElementAt(list.getSelectedIndex()).toString();

//Create a panel that uses BoxLayout.
JPanel pane = new JPanel();
pane.setLayout(new BoxLayout(pane, BoxLayout.LINE_AXIS));
pane.add(deleteButton);
pane.add(Box.createHorizontalStrut(5));
pane.add(new JSeparator(SwingConstants.VERTICAL));
pane.add(Box.createHorizontalStrut(5));
pane.add(ename);
pane.add(hireButton);
pane.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));

add(listScrollPane, BorderLayout.CENTER);
add(pane, BorderLayout.PAGE_END);
}

class DeleteListener implements ActionListener {
public void actionPerformed(ActionEvent e) {

int index = list.getSelectedIndex();
listModel.remove(index);

int size = listModel.getSize();

if (size == 0) { //Nobody's left, disable firing.
deleteButton.setEnabled(false);

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

list.setSelectedIndex(index);
list.ensureIndexIsVisible(index);
}
}
}

//This listener is shared by the text field and the save 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 = ename.getText();

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

int index = list.getSelectedIndex();
if (index == -1) {
index = 0;
} else {
index++;
}

listModel.insertElementAt(ename.getText(), index);

//Reset the text field.
ename.requestFocusInWindow();
ename.setText("");

//Select the new item and make it visible.
list.setSelectedIndex(index);
list.ensureIndexIsVisible(index);
}
protected boolean alreadyInList(String name) {
return listModel.contains(name);
}

//Required by DocumentListener.
public void insertUpdate(DocumentEvent e) {
enableButton();
}

//Required by DocumentListener.
public void removeUpdate(DocumentEvent e) {
handleEmptyTextField(e);
}

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

private void enableButton() {
if (!alreadyEnabled) {
button.setEnabled(true);
}
}

private boolean handleEmptyTextField(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 deleteButton.
deleteButton.setEnabled(false);

} else {
//Selection, enable the deleteButton button.
deleteButton.setEnabled(true);
}
}
}

private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("Single list example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Create and set up the content pane.
JComponent newContentPane = new SingleList();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
frame.setSize(300,200);
frame.setVisible(true);
}

public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
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Read for more information.

http://www.roseindia.net/java/

Thanks.

Amardeep.