Very slow JTextArea updates even as separate thread

Question

Hi,
I am trying to report output of a dynamic stream as a JFrame that contains JTextArea. The module is part of my big SWING application. The problem is JTextArea only shows update after the stream is empty. I have tried the following things
* Stream pocessed as separate thread.
* Thread priority set to maximum.
* function updateUI is called after a batch of lines have been written.
Here's the code to activate the thread
StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "OUTPUT",outputWindow);
outputGobbler.start();Here's the code for StreamGobbler class with JTextArea and JFrame
import java.util.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class StreamGobbler extends Thread
    InputStream is;
    String type;
    String thsContent;
    JTextArea outputWindow;
    StreamGobbler(InputStream is, String type,JTextArea dPane){
        this.is = is;
        this.type = type;
     outputWindow=dPane;
     thsContent=new String("");
    public void run(){
     int myMode=1;
     int lineCt=0;
     String myLineSep=new String(System.getProperty("line.separator"));
        try{
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);
            String line=null;
            while ( (line = br.readLine()) != null){
          if(myMode==1){
              setDisplayWindow();
              myMode=2;
             System.out.println(type + ">" + line);
          outputWindow.append(line+myLineSep);
          lineCt++;
          if(lineCt==10){
              outputWindow.updateUI();
              lineCt=0;
         if(myMode==2)
          outputWindow.updateUI();
     } catch (IOException ioe){
         ioe.printStackTrace(); 
    public void setDisplayWindow(){
     setPriority(MAX_PRIORITY);
     outputWindow=new JTextArea("output",80,300);
     JScrollPane scrollingArea1= new JScrollPane(outputWindow);
     scrollingArea1.setPreferredSize(new Dimension(440, 210));
     scrollingArea1.setMinimumSize(new Dimension(400, 200));
     scrollingArea1.setMaximumSize(new Dimension(1000, 500));
     outputWindow.setEditable(false);
     JFrame displayWindow=new JFrame("Display Window");
     displayWindow.setContentPane(scrollingArea1);
     displayWindow.pack();
     displayWindow.setVisible(true);
}

Answer 1

Thanks for your reply sir.
JDialog won't work for me. I need a JComponent that lets incremental display of content (like append method used in JTextArea).
Below is my example code that you can run and see what I am trying to do. In this example the lines generated by ping are very few. My application actually uses an exe file instead of ping command. The .exe generates few KB of output. I am trying to stream the output of this exe to JTextArea. I am sorry I am not able to provied the actual exe itself.
The example given below works well as the JTextArea gets filled as the output is printed on the command prompt window. It is because of limited resource consumption by ping command. This does not happen with my .exe file. The JTextArea is filled only after the .exe file stops executing. The few hundred lines printed by the .exe file appears suddenly instead of a continuous manner (Although the System.out.println continued to print the output on the command prompt console continuously like the ping example below). Thus there is a delay between the console output and JTextArea when using my exe file.
import java.util.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class StreamGobbler extends Thread
    InputStream is;
    String type;
    String thsContent;
    JTextArea outputWindow;
    StreamGobbler(InputStream is, String type){
        this.is = is;
        this.type = type;
     thsContent=new String("");
    public void run(){
     int myMode=1;
     int lineCt=0;
     String myLineSep=new String(System.getProperty("line.separator"));
        try{
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);
            String line=null;
            while ( (line = br.readLine()) != null){
          if(myMode==1){
              setDisplayWindow();
              myMode=2;
             System.out.println(type + ">" + line);
          ///          thsContent=thsContent.concat(line);
          outputWindow.append(line+myLineSep);
          ///          outputWindow.append();
          lineCt++;
          if(lineCt==1){
              outputWindow.updateUI();
              lineCt=0;
         if(myMode==2)
          outputWindow.updateUI();
     } catch (IOException ioe){
         ioe.printStackTrace(); 
    public void setDisplayWindow(){
     setPriority(MAX_PRIORITY);
     outputWindow=new JTextArea("output",80,300);
     JScrollPane scrollingArea1= new JScrollPane(outputWindow);
     scrollingArea1.setPreferredSize(new Dimension(440, 210));
     scrollingArea1.setMinimumSize(new Dimension(400, 200));
     scrollingArea1.setMaximumSize(new Dimension(1000, 500));
     outputWindow.setEditable(false);
     ///     JPanel myPanel=new JPanel();
     ///     myPanel.add(scrollingArea1);
     JFrame displayWindow=new JFrame("MASPIC Run Window");
     ///     displayWindow.setContentPane(myPanel);
     displayWindow.setContentPane(scrollingArea1);
     displayWindow.pack();
     displayWindow.setVisible(true);
    public static void main(String args[]) {
try{           
            Runtime rt = Runtime.getRuntime();
            Process proc = rt.exec("ping localhost");
            // any error message?
            StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream(), "ERROR");           
            // any output?
         ///            StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "OUTPUT",outputWindow);
            StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "OUTPUT");
            // kick them off
         ///            errorGobbler.start();
            outputGobbler.start();
            // any error???
            int exitVal = proc.waitFor();
            System.out.println("ExitValue: " + exitVal);       
        } catch (Throwable t){
            t.printStackTrace();
}