Java Swing Help

Hi, I am currently using a program called JPadPro for my java source codes. I am just beginning to learn java and I have just started on Java Swing GUI codings. My problem is that the program compiles, but it doesn't run. It always give me an error saying
"Cannot find main method, Program will exit". there is nothing wrong with my source code because I can run somewhere else. I think I didn't configure my Jpadpro correctly. (but anything without GUI does work)
Thank You for your help :)

Even though you are running a swing application, you still need a main method just as in non-GUI applications. The main should create an instance of the JFrame at the base of you swing app. A simple example is as follows:
public class mySwingApp extends JFrame {
public mySwingApp(String title) {
super(title);
// GUI components, layouts, possible listeners here
public static void main(String[] args) {
JFrame mainFrame = new mySwingApp("My first swing app");
mainFrame.setSize(200, 200);
mainFrame.setVisible(true);
}Hope this helps some!
-JBoeing

Similar Messages

Chess: java swing help need

Hi, I have just learn java swing and now creating a chess game. I have sucessfully create a board and able to display chess pieces on the board. By using JLayeredPane, I am able to use drag and drop for the piece. However, there is a problem which is that I can drop the chess piece off the board and the piece would disappear. I have try to solve this problem by trying to find the location that the chess piece is on, store it somewhere and check if the chess piece have been drop off bound. However, I could not manage to solve it. Also, I am very confuse with all these layer thing.
Any suggestion would be very helpful. Thanks in advance
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ChessBoard extends JFrame implements MouseListener, MouseMotionListener
Object currentPosition;
Color currentColor;
Dimension boardSize = new Dimension(600, 600);
JLayeredPane layeredPane;
JPanel board;
JPanel box;
JLabel chessPiece;
int xAdjustment;
int yAdjustment;
public ChessBoard()
// Use a Layered Pane for this this application
layeredPane = new JLayeredPane();
getContentPane().add(layeredPane);
layeredPane.setPreferredSize( boardSize );
     layeredPane.addMouseListener( this );
layeredPane.addMouseMotionListener( this );
// Add a chess board to the Layered Pane
board = new JPanel();
     // set "board" to the lowest layer (default_layer)
layeredPane.add(board, JLayeredPane.DEFAULT_LAYER);
board.setLayout( new GridLayout(8, 8) );
board.setPreferredSize( boardSize );
board.setBounds(0, 0, boardSize.width, boardSize.height);
     addShade();
     addPiece();
public void addShade()
     for (int i = 0; i < 64; i++)
box = new JPanel( new BorderLayout() );
board.add( box, BorderLayout.CENTER );
     if( ((i / 8) % 2) == 0)
               if( (i % 2) ==0)
                    box.setBackground(Color.lightGray);
               } else {
                    box.setBackground( Color.white);
          } else {
               if( (i % 2) ==0)
                    box.setBackground(Color.white);
               } else {
                    box.setBackground(Color.lightGray);
//Method for adding chess pieces to the board
public void addPiece()
// Add a few pieces to the board
     //black pieces
     for (int i = 0; i < 64; i++)
          //adding black pieces
          if (i < 8)
               String fileName = i + ".gif";
               JLabel blackPieces = new JLabel( new ImageIcon( fileName ) );
               JPanel panel = (JPanel)board.getComponent( i );
               panel.add( blackPieces );
          //adding black pones
          if ((i > 7) && (i < 16))
               String fileName = "8.gif";
               JLabel blackPones = new JLabel( new ImageIcon( fileName ) );
               JPanel panel = (JPanel)board.getComponent( i );
               panel.add( blackPones );
          //jump to white position (Component 48)
          if (i == 16) i = 48;
          //adding white pones
          if(( i > 47 ) && (i < 56))
               JLabel whitePones = new JLabel( new ImageIcon("48.gif") );
               JPanel panel = (JPanel)board.getComponent( i );
               panel.add( whitePones );
          //adding white pieces
          if (i > 55)
               String fileName = i + ".gif";
               JLabel whitePieces = new JLabel( new ImageIcon( fileName ) );
               JPanel panel = (JPanel)board.getComponent( i);
               panel.add( whitePieces );
** Add the selected chess piece to the dragging layer so it can be moved
public void mousePressed(MouseEvent e)
chessPiece = null;
Component c = board.findComponentAt(e.getX(), e.getY());
     c.setBackground(Color.red);
if (c instanceof JPanel) return;
Point parentLocation = c.getParent().getLocation();
xAdjustment = parentLocation.x - e.getX();
yAdjustment = parentLocation.y - e.getY();
chessPiece = (JLabel)c;
chessPiece.setLocation(e.getX() + xAdjustment, e.getY() + yAdjustment);
chessPiece.setSize(chessPiece.getWidth(), chessPiece.getHeight());
layeredPane.add(chessPiece, JLayeredPane.DRAG_LAYER);
** Move the chess piece around
public void mouseDragged(MouseEvent me)
if (chessPiece == null) return;
chessPiece.setLocation(me.getX() + xAdjustment, me.getY() + yAdjustment);
** Drop the chess piece back onto the chess board
public void mouseReleased(MouseEvent e)
     Component c = board.findComponentAt(e.getX(), e.getY());
     int x = (int)c.getBounds().getX();
     int y = (int)c.getBounds().getY();
     System.out.println(c.getLocation());
     System.out.println(x + " "+ y);
     c.setBackground(currentColor);
if (chessPiece == null) return;
chessPiece.setVisible(false);
if (c instanceof JLabel)
Container parent = c.getParent();
     //remove the piece that is capture
parent.remove(0);
parent.add( chessPiece );
else
Container parent = (Container)c;
parent.add( chessPiece );
chessPiece.setVisible(true);
public void mouseClicked(MouseEvent e) {}
public void mouseMoved(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
private static void createAndShowGUI()
     //Make sure we have nice window decorations
     JFrame.setDefaultLookAndFeelDecorated(true);
     JFrame frame = new ChessBoard();
     frame.setDefaultCloseOperation( JFrame.DISPOSE_ON_CLOSE );
     //Display the window
     frame.pack();
     frame.setResizable( false );
     frame.setLocationRelativeTo( null );
     frame.setVisible(true);
public static void main(String[] args)
     //Schedule a job for the event-dispatching thread:
     //creating and showing this application's GUI
     javax.swing.SwingUtilities.invokeLater( new Runnable()
               public void run()
                    createAndShowGUI();
}

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ChessBoardRx extends JFrame implements MouseListener, MouseMotionListener
    Object currentPosition;
    Color currentColor;
    Dimension boardSize = new Dimension(600, 600);
    JLayeredPane layeredPane;
    JPanel board;
    JPanel box;
    JLabel chessPiece;
    int xAdjustment;
    int yAdjustment;
    Container lastParent;
    public ChessBoardRx()
        // Use a Layered Pane for this this application
        layeredPane = new JLayeredPane();
        getContentPane().add(layeredPane);
        layeredPane.setPreferredSize( boardSize );
        layeredPane.addMouseListener( this );
        layeredPane.addMouseMotionListener( this );
        // Add a chess board to the Layered Pane
        board = new JPanel();
        // set "board" to the lowest layer (default_layer)
        layeredPane.add(board, JLayeredPane.DEFAULT_LAYER);
        board.setLayout( new GridLayout(8, 8) );
        board.setPreferredSize( boardSize );
        board.setBounds(0, 0, boardSize.width, boardSize.height);
        addShade();
        addPiece();
//        populateBoard();
    public void addShade()
        for (int i = 0; i < 64; i++)
            box = new JPanel( new BorderLayout() );
            board.add( box, BorderLayout.CENTER );
            if( ((i / 8) % 2) == 0)
                if( (i % 2) ==0)
                    box.setBackground(Color.lightGray);
                } else {
                    box.setBackground( Color.white);
            } else {
                if( (i % 2) ==0)
                    box.setBackground(Color.white);
                } else {
                    box.setBackground(Color.lightGray);
    //Method for adding chess pieces to the board
    public void addPiece()
        // Add a few pieces to the board
        //black pieces
        for (int i = 0; i < 64; i++)
            //adding black pieces
            if (i < 8)
                String fileName = i + ".gif";
                JLabel blackPieces = new JLabel( new ImageIcon( fileName ) );
                JPanel panel = (JPanel)board.getComponent( i );
                panel.add( blackPieces );
            //adding black pones
            if ((i > 7) && (i < 16))
                String fileName = "8.gif";
                JLabel blackPones = new JLabel( new ImageIcon( fileName ) );
                JPanel panel = (JPanel)board.getComponent( i );
                panel.add( blackPones );
            //jump to white position (Component 48)
            if (i == 16) i = 48;
            //adding white pones
            if(( i > 47 ) && (i < 56))
                JLabel whitePones = new JLabel( new ImageIcon("48.gif") );
                JPanel panel = (JPanel)board.getComponent( i );
                panel.add( whitePones );
            //adding white pieces
            if (i > 55)
                String fileName = i + ".gif";
                JLabel whitePieces = new JLabel( new ImageIcon( fileName ) );
                JPanel panel = (JPanel)board.getComponent( i);
                panel.add( whitePieces );
    private void populateBoard() {
        int[][] pos = {
            { 9, 7, 5, 1, 3, 5, 7, 9 },
            { 8, 6, 4, 0, 2, 4, 6, 8 }
        for(int j = 0; j < 8; j++) {
            String fileName = "chessImages/" + pos[0][j] + ".jpg";
            JLabel label = new JLabel( new ImageIcon( fileName ) );
            JPanel panel = (JPanel)board.getComponent( j );
            panel.add( label );
        for(int j = 8; j < 16; j++) {
            String fileName = "chessImages/" + 11 + ".jpg";
            JLabel label = new JLabel( new ImageIcon( fileName ) );
            JPanel panel = (JPanel)board.getComponent( j );
            panel.add( label );
        for(int j = 56, k = 0; j < 64; j++, k++) {
            String fileName = "chessImages/" + pos[1][k] + ".jpg";
            JLabel label = new JLabel( new ImageIcon( fileName ) );
            JPanel panel = (JPanel)board.getComponent( j );
            panel.add( label );
        for(int j = 48; j < 56; j++) {
            String fileName = "chessImages/" + 10 + ".jpg";
            JLabel label = new JLabel( new ImageIcon( fileName ) );
            JPanel panel = (JPanel)board.getComponent( j );
            panel.add( label );
     ** Add the selected chess piece to the dragging layer so it can be moved
    public void mousePressed(MouseEvent e)
        chessPiece = null;
        Component c = board.findComponentAt(e.getX(), e.getY());
        c.setBackground(Color.red);
        if (c instanceof JPanel) return;
        lastParent = c.getParent();
        Point parentLocation = c.getParent().getLocation();
        xAdjustment = parentLocation.x - e.getX();
        yAdjustment = parentLocation.y - e.getY();
        chessPiece = (JLabel)c;
        chessPiece.setLocation(e.getX() + xAdjustment, e.getY() + yAdjustment);
        chessPiece.setSize(chessPiece.getWidth(), chessPiece.getHeight());
        layeredPane.add(chessPiece, JLayeredPane.DRAG_LAYER);
     ** Move the chess piece around
    public void mouseDragged(MouseEvent me)
        if (chessPiece == null) return;
        chessPiece.setLocation(me.getX() + xAdjustment, me.getY() + yAdjustment);
     ** Drop the chess piece back onto the chess board
    public void mouseReleased(MouseEvent e)
        Component c = board.findComponentAt(e.getX(), e.getY());
        if(c == null) {
            layeredPane.remove(chessPiece);
            lastParent.add(chessPiece);
            Rectangle r = lastParent.getBounds();
            chessPiece.setLocation(r.x+xAdjustment, r.y+yAdjustment);
            lastParent.validate();
            lastParent.repaint();
            return;
        int x = (int)c.getBounds().getX();
        int y = (int)c.getBounds().getY();
        System.out.println(c.getLocation());
        System.out.println(x + " "+ y);
        c.setBackground(currentColor);
        if (chessPiece == null) return;
        chessPiece.setVisible(false);
        if (c instanceof JLabel)
            Container parent = c.getParent();
            //remove the piece that is capture
            parent.remove(0);
            parent.add( chessPiece );
        else
            Container parent = (Container)c;
            parent.add( chessPiece );
        chessPiece.setVisible(true);
    public void mouseClicked(MouseEvent e) {}
    public void mouseMoved(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}
    private static void createAndShowGUI()
        //Make sure we have nice window decorations
        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new ChessBoardRx();
        frame.setDefaultCloseOperation( JFrame.DISPOSE_ON_CLOSE );
        //Display the window
        frame.pack();
        frame.setResizable( false );
        frame.setLocationRelativeTo( null );
        frame.setVisible(true);
    public static void main(String[] args)
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI
        javax.swing.SwingUtilities.invokeLater( new Runnable()
            public void run()
                createAndShowGUI();
}

Java.io and java.swing help

i'm writing a program that write the byte representation of numbers and outputs them to a joptionpane window
it keeps telling me that void functions are not allowed
is there any way that i can use void functions in my output? or would i need to change to a method that returns a value?
here is my code, please help me, it will be greatly appreciated :)
GUI Part
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class zero2nineTest extends JFrame{
     zero2nine show;
     public static void main(String[] args){
          zero2nineTest x = new zero2nineTest();
          x.setVisible(true);
     public zero2nineTest(){
          super("File IO and Byte Representation Tests");
          Container cp = getContentPane();
          cp.setLayout(new FlowLayout());
          JButton readFile1 = new JButton("Create and Read 1st Byte Representations");
          readFile1.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent e){
                    zero2nine.writeFile(out);
                    JOptionPane.showMessageDialog(
                         zero2nineTest.this,
                         "Odd numbers: " + zero2nine.readFile(), "Byte Representation of Odd Numbers",
                         JOptionPane.PLAIN_MESSAGE);
               cp.add(readFile1);
          JButton readFile2 = new JButton("Create and Read 2nd Byte Representations");
          readFile1.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent e){
                    zero2nine.writeFile2(out);
                    JOptionPane.showMessageDialog(
                         zero2nineTest.this,
                         "Even numbers: " + zero2nine.readFile2(), "Byte Representation of Even Numbers",
                         JOptionPane.PLAIN_MESSAGE);
               cp.add(readFile2);
          JButton quit = new JButton("Quit Program");
          quit.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent e){
                    int decision;
                    decision = JOptionPane.showConfirmDialog(
                         null, "Are you sure?", "Are you sure?", JOptionPane.YES_NO_OPTION);
                         if(decision == 0){
                              System.exit(0);
               cp.add(quit);
               pack();
Class Part
import java.io.*;
class zero2nine{
     static String fileName = "zero2nine.txt";
//     public static void main(String[] args){
//          try{
//               FileOutputStream out = createFile();
//               writeFile(out);
//               writeFile2(out);
//               readFile();
//               readFile2();
//          }catch(IOException io){
//               System.out.println("closing program");
     static FileOutputStream createFile() throws IOException{
          File f = new File(fileName);
          FileOutputStream out = new FileOutputStream(f);
          return out;
     static void writeFile(FileOutputStream out) throws IOException{
          DataOutputStream ds = null;
          try{
               ds = new DataOutputStream(out);
               int x = 0;
               for(int i = 0; i < 10; i++){
                    x = i * i;
                    ds.writeInt(x);
          }finally{
               System.out.println("File written this far");
     static void writeFile2(FileOutputStream out) throws IOException{
          DataOutputStream ds = null;
          try{
               ds = new DataOutputStream(out);
               int x = 0;
               for(int i = 10; i < 20; i++){
                    x = i * i;
                    ds.writeInt(x);
          }finally{
               System.out.println("File written this far again");
     public int readFile() throws IOException{
          DataInputStream dataIn = null;
          try{
               FileInputStream in = new FileInputStream("zero2nine.txt");
               dataIn = new DataInputStream(in);
               //Output odd numbers
               for(int i = 0; i < 10; i++){
                    if(dataIn.readInt() % 2 == 0){
                         int b = dataIn.readInt();
                         System.out.println(b);
          }finally{
               System.out.println("File read this far");
               return(b);
     static void readFile2() throws IOException{
          DataInputStream dataIn = null;
          try{
               FileInputStream in = new FileInputStream("zero2nine.txt");
               dataIn = new DataInputStream(in);
               //Output even numbers
               for(int i = 10; i < 20; i++){
                    if(dataIn.readInt() % 2 == 1){
                         int b = dataIn.readInt();
                         System.out.println(b);
          }finally{
               System.out.println("File read this far again");
}

F:\Computer Science\Java\zero2nineTest.java:28: cannot resolve symbol
symbol: variable out
                    zero2nine.writeFile(out);
^
               public void actionPerformed(ActionEvent e){
                    zero2nine.writeFile(out);
                    JOptionPane.showMessageDialog(
F:\Computer Science\Java\zero2nineTest.java:31: 'void' type not allowed here
                         "Odd numbers: " + zero2nine.readFile(), "Byte Representation of Odd Numbers",
^
                         zero2nineTest.this,
                         "Odd numbers: " + zero2nine.readFile(), "Byte Representation of Odd Numbers",
                         JOptionPane.PLAIN_MESSAGE);
F:\Computer Science\Java\zero2nineTest.java:41: cannot resolve symbol
symbol: variable out
                    zero2nine.writeFile2(out);
^
                    zero2nine.writeFile2(out);
                    JOptionPane.showMessageDialog(
                         zero2nineTest.this,
F:\Computer Science\Java\zero2nineTest.java:44: 'void' type not allowed here
                         "Even numbers: " + zero2nine.readFile2(), "Byte Representation of Even Numbers",
^
                         zero2nineTest.this,
                         "Even numbers: " + zero2nine.readFile2(), "Byte Representation of Even Numbers",
                         JOptionPane.PLAIN_MESSAGE);
4 errors
Tool completed with exit code 1

Help with java swing

Hi people!i need some help
Im a new user for java programming language.Well im programming an application using java swing libraries. I have some problems trying to accesing variables from those swing Jpanels. Ill make it clear....
Im using Netbeans...
I have a class for the window (a JFrame) including 2 Jtextfields and 2 Jlabels
import .......
public class myclass extends javax.swing.JFrame{
public double gp;
public double gv;
public G() {
initComponents();
gpnom=this.gpnom;
gvnom=this.gvnom;
private void TXFgpnom(java.awt.event.ActionEvent evt) { //TXField
gpnom= Double.parseDouble(TXFgpnom.getText());
gvnom= Double.parseDouble(TXFgvnom.getText());
.......//theres a lot of more code .for listeners..next...
Now ive created a new file (a new class)in the same package ,but i cant access public variables from swing class
//the next class was created in a new file
public class hi () {
JPanel prin =(JPanel) new myclass().getContentPane(); //ok
double number=gpnom // error variable not found
When i try to get the value of "number" ...i always get "ERROR" And the class for that textfield was public..i think...
HOw can i use variables from that Jpanel?
Id appreciate an answer...
thanx for your help!
Paco

In future Swing related questions should be posted in the Swing forum and camickr will be more likely to answer if you have used code tags to properly format your code.
Luckily this problem does not seem to be Swing related in the least because the public variables you have in your other class are named gp and gv and further when you access public variables (or properties) of a class you must access them by an instance of that class. Which you don't appear to be doing either.

Need help for connecting Ms Acces with java Swing in Mac OS

Hi all,
i need to connect to Ms Access in MAc os through my java swing program.
Is it possible for accessing Ms access through dsn in Mac OS.
If Possible which driver shall i use for Establishing Connection with MS Access in Mac OS.
Suggestion is needed urgently.
Can anybody help me out regarding this..
Thanks in advance.
Regards,
sreand

if I don't find a better solution I'll try your 2nd option but what do you mean by "combo" update?
My understanding is to simply insert the OS 10.5 installation CD, reinstall the OS and the just keep updating it via the OS SSoftware update panel and stop untill I see the scary Java 8 update. Is that what you meant?
While you can do it that way, the combo update picks up operating system updates through a collection of releases. When dealing with operating system upgrades, I've found using the combo updates to be more reliable than Software Update, as sometimes Software Update doesn't apply updates correctly, and weird things can happen. Doesn't happen often though, thankfully.
So the OS X 10.5.5 Combo update contains all updates between 10.5.0 and 10.5. The 10.5.8 combo update contains the updates from 10.5 thru 10.8. Here are the updates:
10.5 combo update: http://support.apple.com/kb/DL692
10.8 combo update: http://support.apple.com/kb/DL866
If you go down the combo path, repair permissions before and after doing each update. Then do Software Update for any other non-OS X updates, and don't apply the Java Update 8.

Chess: Java Swing problem!! Help need

Hi, I have just learn java swing and now creating a chess game. I have sucessfully create a board and able to display chess pieces on the board. By using JLayeredPane, I am able to use drag and drop for the piece. However, there is a problem which is that I can drop the chess piece off the board and the piece would disappear. I have try to solve this problem by trying to find the location that the chess piece is on, store it somewhere and check if the chess piece have been drop off bound. However, I could not manage to solve it. Also, I am very confuse with all these layer thing.
Any suggestion would be very helpful. Thanks in advance

I wonder if you are biting off a little more than you can chew. This seems like a big project for a beginning coder. Anyway, my suggestions can only be general since we only have general information:
1) Break the big problem down into little pieces. Get the pieces working, then put them together.
2) Make sure your program logic is separate from your GUI.
3) If still having problems, post an SSCCE. See this link to tell you how:
http://homepage1.nifty.com/algafield/sscce.html
4) And as camikr would say (and flounder just said): next time, post this in the Swing forum.
Good luck!

A tiny font is used in many places across Java Swing applications (help!)

In many places in Java but mostly in text boxes I'm seeing a very small font that is quite hard to read.
I am seeing this all over the place in Java programs and it is getting on my nerves.
I'm not sure what is causing this.
I also encountered this issue when running Java on Windows XP.
I really need help on how to solve this,
Or maybe it is actually a bug with Java itself and Windows?
An image of the problem in SwingSet2:
[SwingSet 2 Tiny Font Example|http://img687.imageshack.us/img687/1373/swingset2tinyfont.png]
System spec:
Windows 7 Professional 32-bit (Aero is on)
Java 6 Update 20
English system locale and language
No special dpi settings (default)
Screen Resolution: 1280x1024
Avast Antivirus 5.0
An intel graphics card
Edited by: Temp111 on May 9, 2010 7:38 AM

camickr wrote:
That is not a problem. Somewhere in that code the programmer uses setFont(....) to make it a smaller font. The default font of a text component does not behave like that.
For more help create a [SSCCE (Short, Self Contained, Compilable and Executable, Example Program)|http://sscce.org/], that demonstrates the incorrect behaviour.
Don't forget to use the Code Formatting Tags so the posted code retains its original formatting. That is done by selecting the code and then clicking on the "Code" button above the question input area.No, it's defiantly a problem. Probably in the default fonts that Swing uses in some places.
I detected one place where I can easily trigger this issue, a JTextArea And the Windows Look and Feel, So here is a SSCCE for you:
[Picture Of Tiny Font SSCCE With Tiny Font issue|http://img88.imageshack.us/img88/7876/tinyfont.png]
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TinyFont {
     public static void main(String[] args) {
          try {
               UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
          } catch (ClassNotFoundException e) {
               e.printStackTrace();
          } catch (InstantiationException e) {
               e.printStackTrace();
          } catch (IllegalAccessException e) {
               e.printStackTrace();
          } catch (UnsupportedLookAndFeelException e) {
               e.printStackTrace();
          JFrame frame = new JFrame("Tiny Font");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          JTextArea textArea = new JTextArea("Tiny Font Test");
          frame.add(textArea);
          frame.setSize(150, 100);
          frame.setLocationRelativeTo(null);
          frame.setVisible(true);
}But I also encountered this issue in other places that use Swing.
Try SwingSet2 Source Code Tab for example: [SwingSet2|http://java.sun.com/products/jfc/jws/SwingSet2.jnlp]

Help! how can I update JDK from 1.3 to 1.4 for Java Swing correctly?

Urgent! currently I meet one trouble for GUI display, which is developed by Java Swing when I update my JDK1.3 to 1.4. I use JRun as web server and all of the GUI Java Swing code developed based on JDK 1.3 and before I update, all of the GUI display is correct and there are no problem, but after I update to JDK 1.4, I always meet this kind of problem "java.lang NoClassDefFoundError" which is displaye on Java Console and "Exception:java.lang.NullPintException" is displayed on GUI. Sometimes, I need to try two times to display GUI(Jave Swing), then it can work. Could you give me a fever and show me how to fix this problems? which kind of change in JDK Java Swing package?
Thank you much.
Steven

I have recompiled app. by JDK1.4 and I also changed classpath but I can not fix the problem. The strange thing is that I can view the The same GUI(Java Swing) which is installed in another computer using the same JRUN too, but in local computer I can not view the GUI. Do you have some other suggestions? Why Can I view the same GUI instaaled in another computer?
Very Thanks
Steven

Help! Multi-Thread in Java Swing!

Hi,
I have a java swing application. The basic logic for the application is, I will input some data and click the "Process" Button.
The application will perform some operation. Currently I can perform one operation at a time.
I have to extend the scope of this application to multiple process at the same time.
like, I will add a table in the application. Whenever I give input and press the "Process" button, the process should be added in the table at the same time I should be able to input and initiate the next operation.
I am not very much experienced in java swing.
Is it possible to do in swing? Can somebody give me some input on this?
Thanks,
Raja.

Check out SwingWorker http://docs.oracle.com/javase/7/docs/api/javax/swing/SwingWorker.html

Problem with java swing button and loop

Problem with java swing button and loop
I�m using VAJ 4.0. and I�m doing normal GUI application. I have next problem.
I have in the same class two jswing buttons named start (ivjGStart) and stop (ivjGStop) and private static int field named Status where initial value is 0. This buttons should work something like this:
When I click on start button it must do next:
Start button must set disenabled and Stop button must set enabled and selected. Field status is set to 1, because this is a condition in next procedure in some loop. And then procedure named IzvajajNeprekinjeno() is invoked.
And when I click on stop button it must do next:
Start button must set enabled and selected and Stop button must set disenabled.
Field status is set to 0.
This works everything fine without loop �do .. while� inside the procedure IzvajajNeprekinjeno(). But when used this loop the start button all the time stay (like) pressed. And this means that a can�t stop my loop.
There is java code, so you can get better picture:
/** start button */
public void gStart_ActionEvents() {
try {
ivjGStart.setEnabled(false);
ivjGStop.setEnabled(true);
ivjGStop.setSelected(true);
getJTextPane1().setText("Program is running ...");
Status = 1;
} catch (Exception e) {}
/** stop button */
public void gStop_ActionEvents() {
try {
ivjGStart.setEnabled(true);
ivjGStart.setSelected(true);
ivjGStop.setEnabled(false);
getJTextPane1().setText("Program is NOT running ...");
Status = 0;
} catch (Exception e) {
/** procedure IzvajajNeprekinjeno() */
public void IzvajajNeprekinjeno() { //RunLoop
try {
int zamik = 2000; //delay
do {
Thread.sleep(zamik);
PreberiDat(); //procedure
} while (Status == 1);
} catch (Exception e) {
So, I'm asking what I have to do, that start button will not all the time stay pressed? Or some other aspect of solving this problem.
Any help will be appreciated.
Best regards,
Tomi

This is a multi thread problem. When you start the gui, it is running in one thread. Lets call that GUI_Thread so we know what we are talking about.
Since java is task-based this will happen if you do like this:
1. Button "Start" is pressed. Thread running: GUI_Thread
2. Event gStart_ActionEvents() called. Thread running: GUI_Thread
3. Method IzvajajNeprekinjeno() called. Thread running: GUI_Thread
4. Sleep in method IzvajajNeprekinjeno() on thread GUI_Thread
5. Call PreberiDat(). Thread running: GUI_Thread
6. Check status. If == 1, go tho 4. Thread running: GUI_Thread.
Since the method IzvajajNeprekinjeno() (what does that mean?) and the GUI is running in the same thread and the event that the Start button has thrown isn't done yet, the program will go on in the IzvajajNeprekinjeno() method forever and never let you press the Stop-button.
What you have to do is do put either the GUI in a thread of its own or start a new thread that will do the task of the IzvajajNeprekinjeno() method.
http://java.sun.com/docs/books/tutorial/uiswing/index.html
This tutorial explains how to build a multi threaded gui.
/Lime

Certificate support in Java Swing application

Hi There,
I am new to this Certificate thing and running into issues! Would appreciate for all the help and please ignore for any stupid questions.
Here is my scenario.
1. I do have a client server application and client is a java swing application which connects to a Server application (Using Jetty 4.2.22 as embedded server)
2. Initially, it had a self signed certificate but goal is to support third party certificate (i.e import in the server and then show warning to the client during login)
If somebody has already done this or point me to some example (using Jetty APIs) that would be great help. If not, here is what I am trying to do and some questions.
1. I tried to get some free SSL certificate from the web and imported into the server's KeyStore.
If I do a list from the server using Keystore, this is what it looks like
keytool -list -keystore /tmp/keystore -storepass genview
Keystore type: JKS
Keystore provider: SUN
Your keystore contains 2 entries
self, Dec 3, 2008, PrivateKeyEntry,
Certificate fingerprint (MD5): 0D:58:E8:77:89:09:F8:2B:37:64:37:D5:03:AD:C9:0B
rapid, Jan 6, 2009, trustedCertEntry,
Certificate fingerprint (MD5): 64:9C:EF:2E:44:FC:C6:8F:52:07:D0:51:73:8F:CB:3
QUESTION 1 : why the third party certificate's entry as "trustedCertEntry"? Is it always like this? Do I need to have only one certificate at a time? (If so, just remove the self signed and have 3rd party one)
My Jetty server comes up but when I connect from Client Swing App, the "getServerCertificates()" method only returns one entry i.e self signed one but not the third party one.
I am using like this
URL url = new URL("https://127.0.0.1:port");
HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
conn.connect();
Certificate[] certs = conn.getServerCertificates();
Is not this API supposed to return all the server's certificate?
Please guide me or instruct me what to do.
Thanks,
CRB

Crossposted and answered.

Loading large files in Java Swing GUI

Hello Everyone!
I am trying to load large files(more then 70 MB of xml text) in a Java Swing GUI. I tried several approaches,
1)Byte based loading whith a loop similar to
pane.setText("");
             InputStream file_reader = new BufferedInputStream(new FileInputStream
                       (file));
             int BUFFER_SIZE = 4096;
             byte[] buffer = new byte[BUFFER_SIZE];
             int bytesRead;
             String line;
             while ((bytesRead = file_reader.read(buffer, 0, BUFFER_SIZE)) != -1)
                  line = new String(buffer, 0, bytesRead);
                  pane.append(line);
             }But this is gives me unacceptable response times for large files and runs out of Java Heap memory.
2) I read in several places that I could load only small chunks of the file at a time and when the user scrolls upwards or downwards the next/previous chunk is loaded , to achieve this I am guessing extensive manipulation for the ScrollBar in the JScrollPane will be needed or adding an external JScrollBar perhaps? Can anyone provide sample code for that approach? (Putting in mind that I am writting code for an editor so I will be needing to interact via clicks and mouse wheel roatation and keyboard buttons and so on...)
If anyone can help me, post sample code or point me to useful links that deal with this issue or with writting code for editors in general I would be very grateful.
Thank you in advance.

Hi,
I'm replying to your question from another thread.
To handle large files I used the new IO libary. I'm trying to remember off the top of my head but the classes involved were the RandomAccessFile, FileChannel and MappedByteBuffer. The MappedByteBuffer was the best way for me to read and write to the file.
When opening the file I had to scan through the contents of the file using a swing worker thread and progress monitor. Whilst doing this I indexed the file into managable chunks. I also created a cache to further optimise file access.
In all it worked really well and I was suprised by the performance of the new IO libraries. I remember loading 1GB files and whilst having to wait a few seconds to perform the indexing you wouldn't know that the data for the JList was being retrieved from a file whilst the application was running.
Good Luck,
Martin.

Java swing dynamic forms (in a loop)

Hi All,
Is it possible to dynamically create forms using java swing? What I mean to ask is that if I have the necessary information in a table, like the label and a corresponding text field, I can loop through and create the required number of fields. If I do it this way and when the users add text, will I not lose the ability to access each JTextField through its own variable? Is this possible? Basically, I need to be able to access each field through its own variable to do some additional validations on the text entered, etc. Please let me know, if it is possible through java swing.
Any help in this regard is greatly appreciated.
Thanks.

mrbean1975 wrote:
..Is it possible to dynamically create forms using java swing? If by java swing you mean Java Swing, then yes.

Session in java swing??

Hi friends,
I need to create session in java swing...
I have a client running in swing and can access resources in multi-threaded server. I need to validate user using session. But i don't know how to use session.
User has to login with username & password (authentication verified at server using socket communication).
If successful the login frame vanishes and other options are displayed. user has a feature that he can send files to other
user. so i need to use session for security purpose.
Anyone help me with code
Edited by: sathya_vn on Apr 20, 2008 5:41 PM

Anyone help me with the code-----> u got tat wrong..
I need to know how to use session with java swing. I requested if anyone has such code....
This is a part of my project .
Am using MySQL Database to store username and password.
Cleint side interface has a frame (first frame--frame1) requesting client to provide login information. The login details <username and password> are sent to server. server validates whether the login info are correct or not and return true or false .
If false the frame1 will show a JOptionPane ... message stating that wrong username or password specified.
If true i need to create a session and other operations are done after session validation. I am using ssl socket.
If u want the code then i have post around 300 or more lines..

Writing Urdu in java swing component

Hi firiends,
I am searching out how to write urdu as input in java swing JTextField. I have searched a lot but still i am unable to get right information. So plz guys help me how i do use urdu on java swing JTextField. i will be higly thankful to you..
i am waiting your good reponses .
THANKS
Sahibzada

This forum is exclusively for Sun Java Studio Creator. Please post your queries on appropriate forums to have better discussions :
e.g.
Swing Forum :
http://forum.java.sun.com/forum.jspa?forumID=57
Here are some helpful URLs :
How to Use Text Areas
http://java.sun.com/docs/books/tutorial/uiswing/components/textarea.html
http://java.sun.com/docs/books/tutorial/uiswing/components/textarea.html#contents

Java Swing Help

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