Threads + Swing

Question

Hi folks,
I found the following code here at SDN. The main purpose of this code is to execute an exe-file and to redirect its output to a java Swing JTextArea.
This code works fine. However, if I change...
    public cCallGenerator()
        init();
        initProcess();
    }...to...
    public cCallGenerator()
        init();
        // initProcess(); NOW WE DONT START THE PROCESS HERE
    }and start initProcess() by clicking on the button, the output is NOT(!) redirected to the JTextArea. The exe file is still running.
I guess that I simply misunderstood the concept of threads in java...
Can anybody help me?
Thanks a lot
Christian
Here is the code:
import javax.swing.*;
import org.dom4j.Document;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.io.*;
public class cCallGenerator extends JFrame {
    private JTextArea textArea;
    private JTextField textField;
    private PrintWriter writer;
    public cCallGenerator()
        init();
        initProcess();
    public void init()
        textArea = new JTextArea(20, 80);
        textArea.setEditable(false);
        textField = new JTextField(30);
        textField.addKeyListener(new KeyAdapter()
            public void keyPressed(KeyEvent event) {
                if (event.getKeyCode() == KeyEvent.VK_ENTER)
                    if (writer != null)
                        textArea.setText("");
                        writer.print(textField.getText() + "\r\n");
                        writer.flush();
                        textField.setText("");
        Container container = getContentPane();
        JScrollPane scrollPane = new JScrollPane();
        scrollPane.setViewportView(textArea);
        container.add(scrollPane, BorderLayout.CENTER);
        container.add(textField, BorderLayout.SOUTH);
        JButton start = new JButton("Start");
        container.add(start, BorderLayout.WEST);
                                   start.addActionListener(new ActionListener() {
                                        public void actionPerformed(ActionEvent evt) {
                                             try {
                                                  initProcess();
                                             } catch(Exception e) {
                                                  JOptionPane.showConfirmDialog(null,
                                                            "The following error occured while trying to generate the configuration file: \n\n" + e.getMessage(),
                                                            "XML Error",
                                                            JOptionPane.DEFAULT_OPTION, JOptionPane.ERROR_MESSAGE);     
                                                  System.exit(1);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        textField.grabFocus();
        setVisible(true);
    public static void main(String[] args) {
        new cCallGenerator();
    public void initProcess()
        Runtime rt = Runtime.getRuntime();
        try
            //Process p = rt.exec(new String [] {"cmd", "/C", textField.getText()});
            //textArea.setText("");
            //textField.setText("");
            Process p = rt.exec("panoratio.exe -g -c output.xml -o output.pdi");
            writer = new PrintWriter(p.getOutputStream());
            Thread thread1 = new Thread(new StreamReader(p.getErrorStream()));
            Thread thread2 = new Thread(new StreamReader(p.getInputStream()));
            thread1.start();
            thread2.start();
            System.out.println("Exit Value = " + p.waitFor());
        catch (Exception ex)
            textArea.append(ex.getMessage());
            ex.printStackTrace();
    public class StreamReader implements Runnable
        InputStream is;
        public StreamReader(InputStream is)
            this.is = is;
        public void run()
            try
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                String data;
                while ((data = reader.readLine()) != null)
                    textArea.append(data + "\n");
                reader.close();
            catch (IOException ioEx)
                ioEx.printStackTrace();
}

Answer 1

Thanks for your help!
I still don't really understand why - but if I replace
            thread1.start();
            thread2.start();with
            thread2.start();
            SwingUtilities.invokeAndWait(thread1);it works. So, thanks a lot for your help.
Bye