Develop Reference

How to change Background color of a JButton from a derived class in Java Swing

I have a base class mainframe and i have keeping the JButton as final static Which its BGcolor going to be changed by a extended class of mainframe namely dataframe. Initially i need to set the BGColor of the JButton to red. Then I need to change it to some other colors from the dataframe. I can able to set the BGColor from the mainframe but not from the dataframe(extended class). I've used mainframe.Button_name.setBackground(color.yellow); but still its not changing
`enter code here`
public class mainframe {
final static JButton Button_name = new JButton("Hi");
public static void main(String[] args)
{
public void run()
{
Button_name.setBackground(color.Red); //This is working
}
}
}
class dataframe extends mainframe implements Runnable
{
public void run()
{
//doing other things
while(some condition)
{
if (another_condition)
{
//from here i need to change that Buttons color
// i've tried this
mainframe.Button_name.setBackground(color.yellow); //Not working
}
}
}
}
Kindly anyone help with this issue

So you want to change the state of a UI component from a different thread in a different class. There are multiple ways you might be able to do this, but first, I would start by defining away for those classes to be able to only effect the change you want them to.
Exposing the entire frame, component or even button is not a good idea, people have a habit of changing things you don't want them to, so instead, we define a simple contract which states what they are allowed to do, for example...
public interface Colorable {
public void setColor(Color color);
}
This immediately decouples your code, meaning that any code that wants to change the state of your UI (or change the color of something else) can do so, without relying on the physical implementation.
Thread
First, we're going to have a look at using a Thread to change the UI...
public class ColorChanger {
private Colorable colorable;
public ColorChanger(Colorable colorable) {
this.colorable = colorable;
}
public void start() {
Thread t = new Thread(new Runnable() {
#Override
public void run() {
for (int index = 0; index < 1000; index++) {
if (index % 100 == 0) {
if ((index / 100) % 2 == 0) {
colorable.setColor(Color.GREEN);
} else {
colorable.setColor(Color.RED);
}
}
try {
// This is so you can see the colors changing
Thread.sleep(5);
} catch (InterruptedException ex) {
}
}
System.out.println("Done");
}
});
t.start();
}
}
This is a pretty basic class, it requires an instance of Colorable and will change the state of the color for every 100 counts, based on if it's an even or odd hundred
We use a simple JPanel as our base test class, when you click the button, the ColorChanger is created and started.
public class TestPane extends JPanel implements Colorable {
private JButton btn;
private ColorChanger changer;
public TestPane() {
setLayout(new GridBagLayout());
setBorder(new EmptyBorder(20, 20, 20, 20));
btn = new JButton("I am your button");
add(btn);
btn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (changer == null) {
changer = new ColorChanger(TestPane.this);
changer.start();
}
}
});
}
#Override
public void setColor(Color color) {
if (EventQueue.isDispatchThread()) {
btn.setBackground(color);
} else {
System.out.println("Not in the EDT");
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
setColor(color);
}
});
}
}
}
You will note that the setColor method has a bunch of code in it, this is to ensure that the updates to the UI are executed only from within the context of the Event Dispatching Thread.
SwingWorker
An alternative is to use a SwingWorker, which operates very similarly to a Thread, expect it has the ability to publish content to the EDT
public class ColorChangerWorker extends SwingWorker<Void, Color> {
private Colorable colorable;
public ColorChangerWorker(Colorable colorable) {
this.colorable = colorable;
}
#Override
protected void process(List<Color> chunks) {
colorable.setColor(chunks.get(chunks.size() - 1));
}
#Override
protected Void doInBackground() throws Exception {
for (int index = 0; index < 1000; index++) {
if (index % 100 == 0) {
if ((index / 100) % 2 == 0) {
publish(Color.GREEN);
} else {
publish(Color.RED);
}
}
try {
// This is so you can see the colors changing
Thread.sleep(5);
} catch (InterruptedException ex) {
}
}
System.out.println("Done");
return null;
}
}
You will note here, that when we want to change the color we call publish. The process method is called to let us know that there is more data to be processed, but here, we're only interested in the last change.
And out TestPane...
public class TestPane extends JPanel implements Colorable {
private JButton btn;
private ColorChangerWorker changer;
public TestPane() {
setLayout(new GridBagLayout());
setBorder(new EmptyBorder(20, 20, 20, 20));
btn = new JButton("I am your button");
add(btn);
btn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (changer == null) {
changer = new ColorChangerWorker(TestPane.this);
changer.execute();
}
}
});
}
#Override
public void setColor(Color color) {
if (EventQueue.isDispatchThread()) {
btn.setBackground(color);
} else {
System.out.println("Not in the EDT");
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
setColor(color);
}
});
}
}
}
You will note that the setColor method remains unchanged, this is deliberate, when you test this class, you will note that "Not in the EDT" is never printed, basically meaning we could do away with all that code and just call btn.setBackground(color);, but I want you to see the difference.
The Button...
Now, when I run this code, I get the following output...
Wait a minute, that buttons background is filled?! Actually it is, but many button implementations have a secondary "content area" filling
You can turn this off using something like...
btn.setContentAreaFilled(false);
btn.setOpaque(true);
Which will result in something like...

ImageIcon in JLabel not working

I've been struggling with this problem for weeks to no avail. Other Java forums have not been able to help me with this so I'm hoping I can find someone here with new eyes. I have a JFrame in which, among other things, I am trying to insert an image. I have put together an SSCCE that reproduces the problem.
public class ImageTest {
public static void main(String[] args) {
SplashScreen.ShowWindow();
}
}
public class SplashScreen {
private JFrame frmKcbsEventsSearch;
public SplashScreen() {
initialize();
}
public static void ShowWindow() {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SplashScreen window = new SplashScreen();
window.frmKcbsEventsSearch.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public void initialize() {
frmKcbsEventsSearch=new JFrame();
frmKcbsEventsSearch.getContentPane().setBounds(new Rectangle(200, 200, 520, 450));
frmKcbsEventsSearch.getContentPane().setFont(new Font("Times New Roman", Font.PLAIN, 16));
frmKcbsEventsSearch.setTitle("KCBS Events Search");
frmKcbsEventsSearch.setBounds(200,200,520,450);
frmKcbsEventsSearch.getContentPane().setLayout(new FlowLayout());
frmKcbsEventsSearch.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JLabel logo;
java.net.URL logoURL=getClass().getResource("KCBSLogo.jpg");
if (logoURL!=null) {
try {
logo = new JLabel();
logo.setIcon(new ImageIcon(logoURL));
}
catch (Exception e) {
logo = new JLabel("KCBS Logo");
}
}
else {
logo = new JLabel("KCBS Logo missing");
}
logo.setHorizontalAlignment(SwingConstants.CENTER);
logo.setVerticalAlignment(SwingConstants.CENTER);
frmKcbsEventsSearch.getContentPane().add(logo);
}
}
It has been mentioned elsewhere that the layout is important to make this work. I've not had much luck getting layout managers to do what I want but in this case I just want to get the image displayed. Once I have that I'll work through getting it formatted the way I want.

This code works perfectly fine!
I changed the KCBSLogo.jpg to a source that I had named tile.png.
When I ran it displayed perfectly.
Make sure the KCBSLogo.jpg is in your SRC folder in the project.
http://i.stack.imgur.com/sYfYF.png
As you can see the tile image was shown.

Do Robot methods need to be run on the event queue?

Robot is part of the AWT library, but it seems quite different from most all the rest of the library. I am creating a Swing GUI that mixes Swing with Java Native Access (JNA) and Robot to allow Java to drive some MS Windows/Citrix work programs. My gut feeling is that since Robot will queue events on the "platform's native input queue" that the last thing I want to do is to run it on the EDT, but on the other hand, most of the classes in the AWT and Swing libraries should be run on the Swing event thread. So to try clarify this in my mind for me let me ask as specific a question as possible:
Should Robot methods (in particular key presses and releases, mouse moves, mouse presses and releases) be run on or off of the Swing event dispatch thread (the EDT)?

The Robot methods you mentioned should not be run on the EDT. Taking a look at the source code revealed that each one of these "event" methods has one thing in common (the afterEvent call):
public synchronized void keyPress(int keycode) {
checkKeycodeArgument(keycode);
peer.keyPress(keycode);
afterEvent();
}
public synchronized void mousePress(int buttons) {
checkButtonsArgument(buttons);
peer.mousePress(buttons);
afterEvent();
}
// etc
private void afterEvent() {
autoWaitForIdle();
autoDelay();
}
private void autoWaitForIdle() {
if (isAutoWaitForIdle) {
waitForIdle();
}
}
public synchronized void waitForIdle() {
checkNotDispatchThread();
/* snip */
}
private void checkNotDispatchThread() {
if (EventQueue.isDispatchThread()) {
throw new IllegalThreadStateException("Cannot call method from the event dispatcher thread");
}
}
If you call any of these methods on the EDT while Robot.isAutoWaitForIdle is true, an exception will be thrown. This stands to reason that even if isAutoWaitForIdle is false, these methods shouldn't be called from the EDT.

API quite exactly talks, then I'm understand that that Robot should be ignore if is invoked from EDT or not
Using the class to generate input events differs from posting events to the AWT event queue or AWT components in that the events are generated in the platform's native input queue.
I'm rellative new in Java, my first touch was Java1.6.009, then I can't compare changes for AWT and (when born) Swing in Java1.3 and rest in Java1.4
my example
import javax.imageio.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
public class CaptureScreen implements ActionListener {
private JFrame f = new JFrame("Screen Capture");
private JPanel pane = new JPanel();
private JButton capture = new JButton("Capture");
private JDialog d = new JDialog();
private JScrollPane scrollPane = new JScrollPane();
private JLabel l = new JLabel();
private Point location;
public CaptureScreen() {
capture.setActionCommand("CaptureScreen");
capture.setFocusPainted(false);
capture.addActionListener(this);
capture.setPreferredSize(new Dimension(300, 50));
pane.add(capture);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(pane);
f.setLocation(100, 100);
f.pack();
f.setVisible(true);
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
createPicContainer();
}
});
}
private void createPicContainer() {
l.setPreferredSize(new Dimension(700, 500));
scrollPane = new JScrollPane(l,
ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scrollPane.setBackground(Color.white);
scrollPane.getViewport().setBackground(Color.white);
d.setDefaultCloseOperation(JDialog.HIDE_ON_CLOSE);
d.add(scrollPane);
d.pack();
d.setVisible(false);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("CaptureScreen")) {
Dimension d1 = Toolkit.getDefaultToolkit().getScreenSize(); // gets the screen size
Robot r;
BufferedImage bI;
try {
r = new Robot(); // creates robot not sure exactly how it works
Thread.sleep(1000); // waits 1 second before capture
bI = r.createScreenCapture(new Rectangle(d1)); // tells robot to capture the screen
showPic(bI);
saveImage(bI);
} catch (AWTException e1) {
e1.printStackTrace();
} catch (InterruptedException e2) {
e2.printStackTrace();
}
}
}
private void saveImage(BufferedImage bI) {
try {
ImageIO.write(bI, "JPG", new File("screenShot.jpg"));
} catch (IOException e) {
e.printStackTrace();
}
}
private void showPic(BufferedImage bI) {
ImageIcon pic = new ImageIcon(bI);
l.setIcon(pic);
l.revalidate();
l.repaint();
d.setVisible(false);
location = f.getLocationOnScreen();
int x = location.x;
int y = location.y;
d.setLocation(x, y + f.getHeight());
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
d.setVisible(true);
}
});
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
CaptureScreen cs = new CaptureScreen();
}
});
}
}

Amplifying on #mKorbel's thoughtful answer, and confirming his empirical result, note how the various Robot methods delegate to an internal instance of the RobotPeer interface, the native implementation of which varies by platform. Moreover, the methods are synchronized. The synthetic events all arrive on the EventQueue, irrespective of the source.

Java JFace databinding: Update SWT widget from background thread

A background thread shall update a simple text input field with some value.
I created the POJO with getter/setter in advance, called the JFACE databinding wizard to generate a shell and let it generate the code.
I'm entirely relying on the generated code, just added an inline thread that sets the value data by calling the setter.
While it is working perfectly from the UI to the data POJO, the other way round, no way.
I tried POJOs as well as beans applying PropertyChangeSupport and firePropertyChange(), no way.
Can please somebody shed a light on this or point to some web ressources ? (Sure I googled and applied search here ...)
(For simplicity I've changed some elements to 'static' in this sample as well ommitted some proper thread handling.)
Best regards
Gerd
Code:
public class Gui extends Shell {
private DataBindingContext m_bindingContext;
private static com.gsi.MyDataClass myDataClass = new com.gsi.MyDataClass();
private Text myStringText;
/**
* Launch the application.
* #param args
*/
public static void main(String args[]) {
Display display = new Display();
Realm.runWithDefault(SWTObservables.getRealm(display), new Runnable() {
public void run() {
try {
Display display = Display.getDefault();
Gui shell = new Gui(display, SWT.SHELL_TRIM);
shell.open();
shell.layout();
// here is the thread -----------------------------------------
new Thread () {
public void run () {
while (true) {
try { Thread.sleep(1000); } catch (InterruptedException e) { }
myDataClass.setMyString("Date1:" + new Date().toString());
}
}
} .start();
// the rest is generated code ------------------------------------------------------------
while (!shell.isDisposed()) { if (!display.readAndDispatch()) {
display.sleep(); }
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the shell.
* #param display
* #param style
*/
public Gui(Display display, int style) {
super(display, style);
createContents();
}
/**
* Create contents of the window.
*/
protected void createContents() {
setText("SWT Application");
setSize(242, 99);
setLayout(new GridLayout(2, false));
new Label(this, SWT.NONE).setText("MyString:");
myStringText = new Text(this, SWT.BORDER | SWT.SINGLE);
myStringText.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true,
false));
if (myDataClass != null) {
m_bindingContext = initDataBindings();
}
}
#Override
protected void checkSubclass() {
// Disable the check that prevents subclassing of SWT components
}
public com.gsi.MyDataClass getMyDataClass() {
return myDataClass;
}
public void setMyDataClass(com.gsi.MyDataClass newMyDataClass) {
setMyDataClass(newMyDataClass, true);
}
public void setMyDataClass(com.gsi.MyDataClass newMyDataClass,
boolean update) {
myDataClass = newMyDataClass;
if (update) {
if (m_bindingContext != null) {
m_bindingContext.dispose();
m_bindingContext = null;
}
if (myDataClass != null) {
m_bindingContext = initDataBindings();
}
}
}
protected DataBindingContext initDataBindings() {
DataBindingContext bindingContext = new DataBindingContext();
//
IObservableValue myStringObserveWidget = SWTObservables.observeText(myStringText, SWT.Modify);
IObservableValue myStringObserveValue = PojoObservables.observeValue(myDataClass, "myString");
bindingContext.bindValue(myStringObserveWidget, myStringObserveValue, null, null);
// bindingContext.bindValue(myStringObserveWidget, myStringObserveValue,
// new UpdateValueStrategy(UpdateValueStrategy.POLICY_UPDATE), new UpdateValueStrategy(UpdateValueStrategy.POLICY_UPDATE));
//
return bindingContext;
}
}

PojoObservable is a simple wrap around POJO to use them in databindings. They have no way to check if one of their property change, so there isn't any way they can change the UI in response to change in their internal state.

Use
BeanProperties.value(myDataClass, "myString");
Instead of
PojoObservables.observeValue(myDataClass, "myString");
And your bean setter method must call fireProperyChage(....)

Make a main method wait on a smaller method (java)

i really need to find better ways to word my questions.
Basically I've created a program that takes information from a webpage and displays it nicely across the screen.
When the user closes the program, they actually hide it.
I also have another method which constantly loops checking for information to see if tis been updated.
unfortunately the problem im having is that it loops to fast, i only want it to check for information every 40 seconds or so.
What i tried was inserting a wait(1000,1000) in the method itself and in the main of the program. but both of these cause IllegalMonitorStateException.
Is this the correct way to make the thread wait properly? or is there a better way?
note: the only thread i have is the main.
MAIN
class Marquee
{
public static void main(String[] args) throws InterruptedException
{
MyFrame frame = new MyFrame();
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
frame.setVisible(true);
frame.setAlwaysOnTop(true);
frame.setBackground(Color.BLACK);
frame.setResizable(true);
while(true)
{
// this doesnt work
frame.wait(1000,1000);
frame.notifyAll();
frame.checkForNewUpdate();
System.out.println(" ____________________________next line _______________________________");
}
}
}
CHECK FOR UPDATES
public String[] checkForNewUpdate()
{
//setVisible(true);
String tempUpdate = getEngineersUpdate();
if (latestUpdate[0] != tempUpdate)
{
// do nothign
setVisible(false);
}
else if(latestUpdate[0]==tempUpdate)
{
latestUpdate[0] = tempUpdate;
//show the page again
setVisible(true);
}
else if(latestUpdate[0]!= "NULL")
{
// do nothing
//latestUpdate[0] = tempUpdate;
}
else
{
latestUpdate[0] = tempUpdate;
}
return latestUpdate;
}
1: WHat am i doing wrong to get this exception
2: Is there any other way to make a gap of time in a method
3: Am i going to have to put all these methods into another thread? Please say no
// my constructor which I failed to mention has a timer in it. only i dont know hwo to use it
class MyFrame extends JFrame implements ActionListener
{
private ActionListener listener;
private Timer t1;
private String [] latestUpdate = new String[1];
public MyFrame()
{
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();// gets the maximum size of the screen
setSize(d.width,(d.height/100)*10);//sets it to max. need to change this
// this shit find the max size of screen and puts it bottom left
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice defaultScreen = ge.getDefaultScreenDevice();
Rectangle rect = defaultScreen.getDefaultConfiguration().getBounds();
int x = (int)rect.getMinX();
int y = (int)rect.getMaxY()-getHeight();
setLocation(x,y-30);
setTitle("ALERT::OUTAGE");
MyPanel panel = new MyPanel();
add(panel);
listener = this;
t1 = new Timer(50,listener);
t1.start();
}
by request, here is getEngineersUpdate()
public String getEngineersUpdate() //gets data from page and sets it to string.
{
String update = "blank";
final WebClient webClient = new WebClient();
webClient.setJavaScriptEnabled(false);// javascript causes some serious problems.
webClient.setCssEnabled(false);
String forChecking;
HtmlPage page;
try
{
URL outageURL = new URL("file:\\C:\\Users\\0vertone\\Desktop\\version control\\OUTAGE\\Outages.html"); //local drive at home
page = webClient.getPage(outageURL);
//All this crap can be gone if we just give the table an id
Object[] dates = page.getByXPath("//span[#id='date']/text()").toArray();
Object[] sites = page.getByXPath("//span[#id='site']/text()").toArray();
Object[] issues = page.getByXPath("//span[#id='issue']/text()").toArray();
System.out.println("" + dates[0].toString());
System.out.println("" + sites[0].toString());
System.out.println("" + issues[0].toString());
update = (dates[0].toString() + " " + sites[0].toString() + " " +issues[0].toString());
forChecking = dates[0].toString();
/**some examples of the getCellAt() method*/
//update = table.getCellAt(0,0).asText(); // This returns DATE/Time
//update = table.getCellAt(1,0).asText(); // This return the actual date
//update = table.getCellAt(0,1).asText(); // This returns, SITE/Sector
//update = table.getCellAt(1,1).asText(); // This returns the actual site issue
}
catch (FailingHttpStatusCodeException a)
{
System.out.println("Failing HTTP Status Execution");
a.printStackTrace();
}
catch (MalformedURLException b)
{
System.out.println("Malformed URL");
b.printStackTrace();
}
catch (IOException c)
{
System.out.println("IO PROBLEMS!");
c.printStackTrace();
}
webClient.closeAllWindows();
return update;
}

I've changed your code so it should work as you intended. I'm not clear on what getEngineersUpdate() does, so I can't say for sure if it will work, but I've given you a start. I've included 2 options for how to handle it, with explanation in the comments. You can see how to use a Timer properly in the constructor, also. Finally, I don't have your full code, so I had to rig something together to simulate it.
class Marquee {
public static void main(String[] args) throws InterruptedException {
MyFrame frame = new MyFrame();
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
frame.setVisible(true);
frame.setAlwaysOnTop(true);
frame.setBackground(Color.BLACK);
frame.setResizable(true);
}
}
class MyFrame extends JFrame {
private String [] latestUpdate = new String[1];
private static final int DISPLAY_TIME = 3000;
private Timer displayTimer;
/*
* Option #1:
* Ideally, you'd have the thread that generates the "Engineers Update" messages call this
* method. If you can't make this event based, then you should use option #2
*/
public void newUpdate(String message) {
setVisible(true);
// change this to whatever you need to.
text.setText(message);
displayTimer.restart();
}
// I used this to test it
private JTextField text;
public MyFrame() {
// gets the maximum size of the screen
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
//sets it to max. need to change this
setSize(d.width, (d.height / 100) * 10);
// this shit find the max size of screen and puts it bottom left
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice defaultScreen = ge.getDefaultScreenDevice();
Rectangle rect = defaultScreen.getDefaultConfiguration().getBounds();
int x = (int) rect.getMinX();
int y = (int) rect.getMaxY() - getHeight();
setLocation(x, y - 30);
setTitle("ALERT::OUTAGE");
//MyPanel panel = new MyPanel();
//add(panel);
text = new JTextField("Initial Text");
add(text);
// this creates a timer that when it goes off, will hide the frame
displayTimer = new Timer(DISPLAY_TIME, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
});
// sets the timer not to repeat
displayTimer.setRepeats(false);
//This code is for option #2:
updateTimer = new Timer(UPDATE_INTERVAL, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
checkForNewUpdate();
}
});
updateTimer.start();
}
// This is for option #2
private static final int UPDATE_INTERVAL = 1000;
private Timer updateTimer;
/*
* Option #2:
* Not ideal, but this should work.
*/
public String[] checkForNewUpdate() {
// I don't know how getEngineersUpdate() works
// which would have made it much easier to help you.
String tempUpdate = getEngineersUpdate();
// String comparison doesn't work like this in java.
// you also had a sleeping NullPointerException here
if (!tempUpdate.equals(latestUpdate[0])) {
// this is when you have a new update, correct?
newUpdate(tempUpdate);
latestUpdate[0] = tempUpdate;
} else if (tempUpdate.equals(latestUpdate[0])) {
// it's the same update as last time, so do nothing
} else if (tempUpdate.equals("NULL")) {
// You need to handle this according to what getEngineersUpdate() does
}
return latestUpdate;
}
// This code is rigged to show how it would work
private static int i = 0;
private String getEngineersUpdate() {
// 1 in 6 chance of returning "NULL"
if (Math.random() * 6 - 1 < 0)
return "NULL";
// probability of 1 in 4 of generating a new update
if(Math.random() * 4 - 1 < 0)
return "UPDATE #"+i++;
else
return "UPDATE #"+i;
}
}

I think you can't call wait() on an JFrame, but I am not sure.
You have to call wait() within a snychronized-block. (Example below)
Thread.sleep(1000l) can be used, if it runs in a Thread, but look for the class Timer
It would be much better design, if you create a thread, which checks for updates. You can notify the GUI (JFrame) with some kind of event-listener about the new date to display.
Take a look at the Timer and Callable.

You should create another thread, you should call checkforNewUpdate method from this thread. And also do not forget use SwingUtilities.invokeLater method to update your UI inside checkforNewUpdate method. here is the some part of the code;
public class Marque {
private JFrame frame;
class CheckForUpdate implements Runnable {
public void run() {
while(true) {
checkForNewUpdate();
try {
Thread.sleep(40000);
} catch (InterruptedException e1) {
e1.printStackTrace();
throw new RuntimeException(e1);
} }
}
public String[] checkForNewUpdate() {
//your code
// user interface interaction code
SwingUtilities.invokeLater(new Runnable() {
public void run() {
frame.setVisible(true);
}
});
}
}
public Marque() {
frame = new JFrame();
//....frame related code
new Thread(new CheckForUpdate()).start();
}
public static void main(String[] arg) {
Marque marque = new Marque();
}