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Editorial Team
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Asked: 2026-05-31T07:55:09+00:00

I have a Java Applet compiled in Eclipse using Swing. See here: http://www.test.world2build.com/Game/Play.aspx For

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I have a Java Applet compiled in Eclipse using Swing. See here: http://www.test.world2build.com/Game/Play.aspx

For the start of the applet, I made a “Loading…” dialog that would login and download updates. This applet contains three classes:

  • MainApplet
  • LoadingDialog
  • Connect

MainApplet.class

public class MainApplet extends JApplet {
public MainApplet() {
}
public void init() {
    // constructor 

    setSize(800,600);
    getContentPane().setLayout(null);

    AppSettings AppSettings = new AppSettings();
    AppSettings.Username = GetParameter(0);
    AppSettings.Password = GetParameter(1);
    AppSettings.ClientMode = GetParameter(2);
    AppSettings.ServerIP = GetParameter(3);

    System.out.println("Main applet loaded.");
    System.out.println("Starting load...");

    LoadingDialog load = new LoadingDialog();
    load.setVisible(true);
    getContentPane().add(load);

    int panelX = (getWidth() - load.getWidth() - getInsets().left - getInsets().right) / 2;
    int panelY = ((getHeight() - load.getHeight() - getInsets().top - getInsets().bottom) / 2);
    load.setLocation(panelX, panelY);



    load.lblNewLabel_1.setText("Connecting...");

    //wait(2);

    // UPDATE PROGRESS BAR //
    load.progressBar.setValue(15);

    Connect connect = new Connect();
    String Result = null;
    try {
        Result = connect.Read("http://www.world2build.com/");
    } catch (IOException e) {
        e.printStackTrace();
    }

    if(Result == null) {
        return;
    }

    // UPDATE PROGRESS BAR //
    load.progressBar.setValue(30);

    load.lblNewLabel_1.setText("Checking for updates...");

    //wait(1);

    String UpdatesAvailable = "null";

    try {
        UpdatesAvailable = connect.Read("http://test.world2build.com/Game/CheckUpdates.aspx?v=" + AppSettings.Version);
    } catch (IOException e) {
        e.printStackTrace();
    }

    // UPDATE PROGRESS BAR //
    load.progressBar.setValue(60);

    if(UpdatesAvailable.startsWith("available")) {
        load.lblNewLabel.setText("Updating, please wait...");
        load.lblNewLabel_1.setText("Downloading...");

        URL url;
        try {
            url = new URL("http://www.world2build.com/Game/WorldToBuild.zip");

            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            InputStream in = connection.getInputStream();
            FileOutputStream out = new FileOutputStream(System.getenv("APPDATA") + "download.zip");
            copy(in, out, 1024);
            out.close();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    else if(UpdatesAvailable.startsWith("unavailable")) {
        load.lblNewLabel.setText("Please wait...");
        load.lblNewLabel_1.setText("Logging in...");
        String loginStatus = null;

        try {
            loginStatus = connect.Read(
                    "http://test.world2build.com/Game/Login.ashx?u="
                    + AppSettings.Username + "&p="
                    + AppSettings.Password + "&sip="
                    + AppSettings.ServerIP);
        } catch (IOException e) {
            e.printStackTrace();
        }

        if(loginStatus.startsWith("success")) {
            load.lblNewLabel_1.setText("Connecting...");
            load.progressBar.setValue(100);

            // Join the game. Start game now. //


        }
        else if(loginStatus.startsWith("failed")) {
            load.lblNewLabel.setText("An error occured");
            load.lblNewLabel_1.setText("Login failed.");
        }
        else {
            load.lblNewLabel.setText("An error occured");
            load.lblNewLabel_1.setText("Failed to connect.");
        }
    }
    else {
        load.lblNewLabel.setText("An error occured");
        load.lblNewLabel_1.setText("Failed to check updates.");
    }
}
public static void copy(InputStream input, OutputStream output, int bufferSize) throws IOException {
    byte[] buf = new byte[bufferSize];
    int n = input.read(buf);
    while (n >= 0) {
      output.write(buf, 0, n);
      n = input.read(buf);
    }
    output.flush();
 }
 public static void wait(int n){
    long t0, t1;
    t0 =  System.currentTimeMillis();
    do{
        t1 = System.currentTimeMillis();
    }
    while ((t1 - t0) < (n * 1000));
}
public String GetParameter(int Index) {
    String Parameters = null;
    String[] Stuff = null; 

    try {
        Parameters = this.getParameter("data");
        Stuff = Parameters.split(" ");

        return Stuff[Index];
    } catch(NullPointerException e) {
        e.printStackTrace();
    }

    // Username         Password        ServerMode       IP
    Parameters = "Bailey 1f6311d6446e2a3fa08a1c08187129ad false 127.0.0.1:45565";
    Stuff = Parameters.split(" ");

    return Stuff[Index];
} }

LoadingDialog.class

public class LoadingDialog extends JApplet {

public JPanel frame = new JPanel();

public JProgressBar progressBar;
public JLabel lblNewLabel_1;
public JLabel lblNewLabel;
private JPanel panel;

public LoadingDialog() {
    getContentPane().setFocusable(false);
    frame.setBorder(new LineBorder(new Color(0, 0, 0)));
    setSize(350,150);
    frame.setSize(350,150);
    getContentPane().setLayout(null);
    setVisible(true);
    progressBar = new JProgressBar();
    progressBar.setVerifyInputWhenFocusTarget(false);
    progressBar.setOpaque(true);
    progressBar.setBounds(10, 51, 322, 19);
    getContentPane().add(progressBar);

    lblNewLabel = new JLabel("Please wait...");
    lblNewLabel.setFont(new Font("Tahoma", Font.BOLD, 14));
    lblNewLabel.setBounds(24, 11, 308, 29);
    getContentPane().add(lblNewLabel);

    lblNewLabel_1 = new JLabel("Checking for updates...");
    lblNewLabel_1.setForeground(UIManager.getColor("InternalFrame.borderDarkShadow"));
    lblNewLabel_1.setHorizontalAlignment(SwingConstants.RIGHT);
    lblNewLabel_1.setHorizontalTextPosition(SwingConstants.RIGHT);
    lblNewLabel_1.setBounds(10, 76, 322, 19);
    getContentPane().add(lblNewLabel_1);



    int panelX = (getWidth() - frame.getWidth() - getInsets().left - getInsets().right) / 2;
    int panelY = ((getHeight() - frame.getHeight() - getInsets().top - getInsets().bottom) / 2);
    frame.setBounds(350, 150, panelX, panelY);

    frame.setVisible(true);
} }

For some odd reason, in MainApplet where it gets the contents of URLs using the Connect class (see below), the Applet does not show the LoadingDialog GUI until all is complete.

Connect.class

public class Connect {
public String Read(String theurl) throws IOException {
    URL url = new URL(theurl);

    // Read all the text returned by the server
    BufferedReader in;
    try {
        in = new BufferedReader(new InputStreamReader(url.openStream()));
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
    String str = in.readLine();
    String newstr = "...";

    while(newstr != null) {
        newstr = in.readLine();
        if(newstr == null) {
            break;
        }
        else {
            str += newstr;
        }
    }

    in.close();
    return str;
} }
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1 Answer

  1. Editorial Team

    Your Connect class uses blocking I/O, which is preventing the init method from completing until after everything is downloaded. The Applet won’t render until at least after the init method returns. To allow the init method to return quickly, you could offload the download of resources to a background worker thread.

    See, for example, SwingWorker, which is a utility class designed to help do this kind of worker thread offloading correctly in a Swing GUI. It was introduced as part of standard Java in Java 6. If you need to support Java 5, you can find earlier versions of SwingWorker for download.

    Alternatively you could spawn your own thread. Just be sure to push GUI updates onto the AWT event dispatch thread.

    public class MainApplet extends JApplet {
    public MainApplet() {
    }
    public void init() {
        // constructor 

        setSize(800,600);
        getContentPane().setLayout(null);

        AppSettings AppSettings = new AppSettings();
        AppSettings.Username = GetParameter(0);
        AppSettings.Password = GetParameter(1);
        AppSettings.ClientMode = GetParameter(2);
        AppSettings.ServerIP = GetParameter(3);

        System.out.println("Main applet loaded.");
        System.out.println("Starting load...");

        final LoadingDialog load = new LoadingDialog();
        load.setVisible(true);
        getContentPane().add(load);

        int panelX = (getWidth() - load.getWidth() - getInsets().left - getInsets().right) / 2;
        int panelY = ((getHeight() - load.getHeight() - getInsets().top - getInsets().bottom) / 2);
        load.setLocation(panelX, panelY);

        load.lblNewLabel_1.setText("Connecting...");

        // UPDATE PROGRESS BAR //
        load.progressBar.setValue(15);

        Thread thread = new Thread() {
            public void run() {
                Connect connect = new Connect();
                String Result = null;
                try {
                    Result = connect.Read("http://www.world2build.com/");
                } catch (IOException e) {
                    e.printStackTrace();
                }

                if(Result == null) {
                    return;
                }

                // UPDATE PROGRESS BAR //
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        load.progressBar.setValue(30);
                        load.lblNewLabel_1.setText("Checking for updates...");
                    }
                });

                String UpdatesAvailable = "null";

                try {
                    UpdatesAvailable = connect.Read("http://test.world2build.com/Game/CheckUpdates.aspx?v=" + AppSettings.Version);
                } catch (IOException e) {
                    e.printStackTrace();
                }

                // UPDATE PROGRESS BAR //
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        load.progressBar.setValue(60);
                    }
                });

                if(UpdatesAvailable.startsWith("available")) {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            load.lblNewLabel.setText("Updating, please wait...");
                            load.lblNewLabel_1.setText("Downloading...");
                        }
                    });

                    URL url;
                    try {
                        url = new URL("http://www.world2build.com/Game/WorldToBuild.zip");

                        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                        connection.setRequestMethod("GET");
                        InputStream in = connection.getInputStream();
                        FileOutputStream out = new FileOutputStream(System.getenv("APPDATA") + "download.zip");
                        copy(in, out, 1024);
                        out.close();
                    } catch (MalformedURLException e) {
                        e.printStackTrace();
                    } catch (ProtocolException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                else if(UpdatesAvailable.startsWith("unavailable")) {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            load.lblNewLabel.setText("Please wait...");
                            load.lblNewLabel_1.setText("Logging in...");
                        }
                    });
                    String loginStatus = null;

                    try {
                        loginStatus = connect.Read(
                                "http://test.world2build.com/Game/Login.ashx?u="
                                + AppSettings.Username + "&p="
                                + AppSettings.Password + "&sip="
                                + AppSettings.ServerIP);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }

                    if(loginStatus.startsWith("success")) {
                        SwingUtilities.invokeLater(new Runnable() {
                            public void run() {
                                load.lblNewLabel_1.setText("Connecting...");
                                load.progressBar.setValue(100);
                            }
                        });

                        // Join the game. Start game now. //


                    }
                    else if(loginStatus.startsWith("failed")) {
                        SwingUtilities.invokeLater(new Runnable() {
                            public void run() {
                                load.lblNewLabel.setText("An error occured");
                                load.lblNewLabel_1.setText("Login failed.");
                            }
                        });
                    }
                    else {
                        SwingUtilities.invokeLater(new Runnable() {
                            public void run() {
                                load.lblNewLabel.setText("An error occured");
                                load.lblNewLabel_1.setText("Failed to connect.");
                            }
                        });
                    }
                }
                else {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            load.lblNewLabel.setText("An error occured");
                            load.lblNewLabel_1.setText("Failed to check updates.");
                        }
                    }

                }
            }

            Connect connect = new Connect();
            String Result = null;
            try {
                Result = connect.Read("http://www.world2build.com/");
            } catch (IOException e) {
                e.printStackTrace();
            }

            if(Result == null) {
                return;
            }

            // UPDATE PROGRESS BAR //
            SwingUtilities.invokeLater(new Runnable() {
                public void run() {
                    load.progressBar.setValue(30);
                    load.lblNewLabel_1.setText("Checking for updates...");
                }
            });

            //wait(1);

            String UpdatesAvailable = "null";

            try {
                UpdatesAvailable = connect.Read("http://test.world2build.com/Game/CheckUpdates.aspx?v=" + AppSettings.Version);
            } catch (IOException e) {
                e.printStackTrace();
            }

            // UPDATE PROGRESS BAR //
            SwingUtilities.invokeLater(new Runnable() {
                public void run() {
                    load.progressBar.setValue(60);
                }
            });

            if(UpdatesAvailable.startsWith("available")) {
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        load.lblNewLabel.setText("Updating, please wait...");
                        load.lblNewLabel_1.setText("Downloading...");
                    }
                });

                URL url;
                try {
                    url = new URL("http://www.world2build.com/Game/WorldToBuild.zip");

                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    InputStream in = connection.getInputStream();
                    FileOutputStream out = new FileOutputStream(System.getenv("APPDATA") + "download.zip");
                    copy(in, out, 1024);
                    out.close();
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (ProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            else if(UpdatesAvailable.startsWith("unavailable")) {
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        load.lblNewLabel.setText("Please wait...");
                        load.lblNewLabel_1.setText("Logging in...");
                    }
                });
                String loginStatus = null;

                try {
                    loginStatus = connect.Read(
                            "http://test.world2build.com/Game/Login.ashx?u="
                            + AppSettings.Username + "&p="
                            + AppSettings.Password + "&sip="
                            + AppSettings.ServerIP);
                } catch (IOException e) {
                    e.printStackTrace();
                }

                if(loginStatus.startsWith("success")) {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            load.lblNewLabel_1.setText("Connecting...");
                            load.progressBar.setValue(100);
                        }
                    });

                    // Join the game. Start game now. //


                }
                else if(loginStatus.startsWith("failed")) {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            load.lblNewLabel.setText("An error occured");
                            load.lblNewLabel_1.setText("Login failed.");
                        }
                    });
                }
                else {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            load.lblNewLabel.setText("An error occured");
                            load.lblNewLabel_1.setText("Failed to connect.");
                        }
                    });
                }
            }
            else {
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        load.lblNewLabel.setText("An error occured");
                        load.lblNewLabel_1.setText("Failed to check updates.");
                    }
                });
            }
        }
        thread.start();
    }
    // ...
}
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