Help with displaying output of javac

Question

Hi, I got some code from this forum that helped me
to implement buttons with Action for compiling java code. Any output or exception generated can be displayed to JTextArea.
However, just found out the code I got hangs in cases
when there seems to be lots of exception in source code. (i.e. Nothing displayed on JTextArea )
I list the code below, can someone tell me what I need to do to display output in JTextArea properly??
/* Usage
java OutputCapture javac MyClass.java
java OutputCapture java MyClass
import java.io.*;
import java.util.*;
import javax.swing.*;
public class OutputCapture {
public static void main(String[] args)
JFrame frame = new JFrame();
JPanel panel = new JPanel();
JTextArea tArea = new JTextArea("",8,20);
tArea.setLineWrap(true);
tArea.setWrapStyleWord(true);
JScrollPane pane = new JScrollPane(tArea);
panel.add(pane);
frame.getContentPane().add(panel);
frame.setSize(300,300);
frame.setVisible(true);
String runString = "c:\\java\\bin\\"+ args[0]+ ".exe " + args[1] + "";
String output;
try
Process p = Runtime.getRuntime().exec(runString);
Vector streams = new Vector();
streams.addElement(p.getInputStream());
streams.addElement(p.getErrorStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(new SequenceInputStream(streams.elements())));
while ((output = reader.readLine()) != null)
tArea.append(output + "\n");
reader.close();
catch(Exception e) { e.printStackTrace(); }
</pre>
* Can someone please list the code for displaying
output of compiling/runnning app with Runtime.exe()
command in JTextArea properly? (this is driving me
nut)
Thanks
Okidoki

Answer 1

Hi
I tried your code and it still doesn't work.
It simple hangs there now without output to
screen. Can you be more specific? I have
provided your code below and a class with
bug to be compiled by your code.
Can you show me how the output of compiling can
be shown to screen or to a file through
your method?
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class Exec {
     public Exec(String app) throws Exception {
          Process process = null;
          //final OutputStream out;
          final InputStream err, out;
          process = Runtime.getRuntime().exec(app);
          //out = process.getOutputStream();
          out = process.getInputStream();
          err = process.getErrorStream();
          Runnable r = new Runnable() {
               public void run() {
                    Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
                    try {
                         while(true) {
                              int i = out.available();
                              int j = err.available();
                              if(i > 0) {
                                   byte[] b = new byte;
                                   out.read(b);
                                   //System.err.write(b);
                                   System.err.println(b);
                              if (j > 0) {
                                   byte[] b = new byte[j];
                                   err.read(b);
                                   //System.err.write(b);
                                   System.err.println(b);
                         } // while
                    } catch (IOException e) {
                         System.err.println(e);     
          new Thread(r).start();
          process.destroy();
     public static void main(String[] args) {
          try {
               //String s = "c:\\JBuilder5\\jdk1.3\\bin\\javac.exe FontColorDialog.java";
               String s = "c:\\JBuilder5\\jdk1.3\\bin\\javac.exe test2.java";
               new Exec(s);
          } catch (Exception e) {
               System.err.println(e);
//==================================
// Testing class
//import javax.swing.*; // Uncommented here on purpose
public class test2 {
     public static void main( String args[] ) {
          System.out.println("Hello World!");
          JTextField jtf = new JTextField();
          System.out.println("Font: " + jtf.getFont().toString() );
Thanks