How JTextArea may receive System.out events?

Dear JDevelopers,
How JTextArea may receive System.out events?
It's only have append method which receive string as input parameter.
I want to create GUI application which will show loggin which, by default, directed into System.out, but I want to redirect it in JTextArea.
How can I implement it easy? I don't want to write listeners and events.

Swing related questions should be posted in the Swing forum. Search the forum other discussions on this topic. You can start by using "setOut" as a keyword. You may want add "console" as a second keyword to the narrow the search.

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How do I get System.out.format to print out doubles with the same precision

Using the System.out.format, how do I print out the value of a double such that it looks exactly like it does if it were print from a System.out.println.
For example, take the following code:
double d = 12.48564734342343;
System.out.format("d as format: %f\n", d);
System.out.println("d as sout: " + d);Running the code, I get:

d as format: 12.485647
d as sout: 12.48564734342343

The precision of d has been lost.
I could bump up the precision as follows:
double d = 12.48564734342343;
System.out.format("d as format: %.14f\n", d);
System.out.println("d as sout: " + d);That appears to work, I get:

d as format: 12.48564734342343
d as sout: 12.48564734342343

However, that solution fails if d has a different precision, say 12.48. In that case I get:

d as format: 12.48000000000000
d as sout: 12.48

So how do I get System.out.format to print out doubles with the same precision as System.out.println?
Thanks..

YoungWinston wrote:
Schmoe wrote:
Interesting, but this is not what I am looking for...Your original question was "how do I print out the value of a double such that it looks exactly like it does if it were print from a System.out.println", and you've been told how to do that (although the pattern given by sabre may be a bit excessive - you should only need 15 '#'s).The initial phrase from my question was "Using the System.out.format, how do I..".
It's worth remembering that, unlike the Format hierarchy, 'format()' is NOT native to Java. It's a convenience implementation of the 'printf()' and 'sprintf()' methods provided in C, and first appeared in Java 1.5. Those methods were designed to produced fixed-format output; 'println()' was not.Perhaps it is the case that this can't be done.
Furthermore, Double.toString(), which is what is used by println() does not produce the same format in all cases; format("%.14f\n", d) does. TrySystem.out.println(1.8236473845783d);
System.out.println(1823647384.5783d);and you'll see what I mean.I am fine with that. It still displays all the precision.
I am simply looking for a way to quickly print out multiple variables on a sysout while debugging. I want it as syntactically sweet as possible. System.out.println can be a pain when outputting multiple variables like the following:
"System.out.println("a: " + a + "; b:" + b + "; c: " + c);"
For some reason, my fingers always typo the plus key.
I was hoping that System.out.format would be easier,along the lines of:
"System.out.format("a: %f, b: %f, c: %f\n", a, b, c);"
From a syntactical sweetness point of view, it is easier. However, the %f on doubles truncates the precision. I figured there must be a way to get the full precision.
DecimalFormat is syntactically sour for this purpose, as you need to instantiate the DecimalFormat.
fwiw I have enjoyed reading the suggestions in this thread...

How to :Logging or System.out.println????

Hi,
Iam not able to see any System.out.println output in SAP? where exactly can i see it? any configuration required to enable logging? if so how?? please help

Hi Sujesh,
see https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.km.cm.docs/library/events/webinars/using logging and tracing on the sap web as java.pdf pages 12-17 and pages 22-24.
Also see http://help.sap.com/saphelp_nw04/helpdata/en/e2/75a74046033913e10000000a155106/frameset.htm for portal specific logging issues.
Hope it helps
Detlev

How does one intercept System.out.println stream.

If you want some functionality wherein when you call System.out.println - the stream gets written to System.out AND additionally does something else (e.g. send mail).
AND
You do not want to write a new class/method to do so and replace all System.out.println in your source base with this new class/method;
Then how would you be able to achieve this. Thanks in advance.

Here is the basic code, you may need to tune performance. I havent compiler or tested it, but it should give you a good idea.
public class OutputStreamCollection extends OutputStream{
private OutputStream[] outs = new OutputStream[0];
public synchronized void addOutputStream(OutputStream argOut) {
OutputStream[] old = outs;
outs = new OuputStream[old.length + 1];
System.arraycopy(old,0,outs,0, old.length);
outs[outs.length - 1] = argOut;
public syncrhonized void write(int data) {
for(int i = 0; i < outs.length; i++) {
outs.write();
public synchronized void write(byte[] data, int offset, int length) {
for(int i = 0; i < outs.length; i++) {
outs[i].write(data, offset, length);
nor the following code, will print and log to respective files whatever is going to stdout or stderr
OutpputStreamCollection out = new OutputStreamCollection();
out.addOutputStream(System.out);
out.addOutputStream(new FileOutputStream("stdout.log"));
System.setOut(out);
OutpputStreamCollection err = new OutputStreamCollection();
out.addOutputStream(System.err);
out.addOutputStream(new FileOutputStream("stderr.log"));
System.setOut(err);
you can write adapter classes to process the stream in any way you need, like logging with log4J, or sending mail depending on some crieteria.
Hope it helps.

How do you change system.out.println colour?

Hi, I am developing some basic rmi client/server applications, I have an 2D array on a central server being read/written by remote clients. all the development is using system.out. statements at the moment (hopefully being replaced by GUI later) my question is when a client remote calls a read operation, and reads an array location, eg x3, y4 I want to print the location contents in a different colour to indicate the read, at the moment the displayArray() simply has nested for loops to cycle through the array and System.out.println statements to get it to the screen. I wonder is there a simple way to change the colour of system.out type statements? thanks for any help

I could be wrong, but I don't think that is possible. The System.out and other streams are just streams of characters, and doesn't contain any data about the characters. You could possibly get it to work if you knew which terminal the stream was going to and if the terminal had escape commands that could set colors. BBS browsers have that functionality, but I think that would be a hard path to follow.
If you are printing out a lot of data and need some color to aid it's readability, try printing directly to your graphic context:
Graphics g = getGraphics();
g.setColor(Color.white);
g.drawString("Hello",100,100);

How do you overwrite System.out.print()

I am sure there is a way to over write the last entry to System.out.print ?
I think it is by using an escape sequence (eg \t or \n), but cant work out which letter to use.
can any one help?
Simon

It's \r:
class Overwrite {
     public static void main(String[] args) {
          System.out.print("Old Text");
          System.out.print("\rNew");
}

How to overcome a "System out of memory exception"?

Hi,
As i am running my program , I get (sometimes) an out of memory exception.
I don't know exactly why because I am always doing the same thing so if I get this exception once It should always be so... (of course, as I am trying , no other program is running on my computer! ).
anyway.
I have 3 questions:
1) Do you know how to eliminate this error ?
(I don't mind if the time of execution is longer)
2) I have Win XP, do you think that using a software to build ".exe" files can change the problem ? If so, have you heard about a simple 'one' (I downloaded JET Excelsior, but it seems rather complicated to parametrize)
3) (last but not least) Can someone explain to me WHY there is this type of exception ( I would have thought that when "memory is full", then there is a swap, and the program doesn't stop !
I know there is a lot of questions in one ! ( altough I tried to be short)
Thanks

In answer to your third question, the error occurs when
the JVM runs out of memory, not the OS. Since the OS
controls swapping the fact that the memory space
assigned to the JVM is running low won't cause
swapping to take place. The solution is either a) use
less space by reducing what you have loaded at any
given time or b) increase the amount of memory
available to the JVM. You can user the -Xms, -Xmx and
-Xss switches to increase the amount of memory
available.
Mark

How to capture System.out, done by another program

Hi All,
My application runs other application in back. How can I capture system.out.println() written by another application & display via dialog box.
Like :execl() or execv() function in C runtime library. Where every printf() message printed to passed buffer.
Thank you,
Avin Patel

You can create an InputStream from a started process. Then read all the bytes from the inputstream and write them to an outputstream (like System.out)
Process p = Runtime.getRuntime().exec(COMMAND);
InputStream is = p.getErrorStream(); //Or another stream
int[] buffer = new int[128];
while((read = is.read(buffer)) != -1){
System.write.out(buffer, 0, read);
}

System.out console in GUI

hi i'm constructing a GUI for one of my programs using the swing librarys however i cant figure out how to display the system.out's. I really have no idea how to do it or i would post how im trying to or usual if anyone knows a better way to print strings (an undetermined number of strings this is) to a GUI please let me know

Hi,
Why are you using System.out combined with Swing? Just print text to some text component instead (e.g. JTextArea, see the javadoc for that class for more info)
Kaj

System.out from Java class not output to JSP

I am using JSP to make a Java API web accessible. I include (package) java classes that write error messages to standard out when they catch an error. Works fine on the command line. Problem occurs when using in JSP. I include them with a page directive (importing the package) rather than use them as beans, since they do so much more than beans do, and since I use many of the classes in a single page.
i.e.
<%@ page import="OPS.*" %>
When errors occur, messages to "standard out" (system.out) don't appear in the html output of the JSP. I don't know where they are going (they aren't in the web server's error log), but they aren't going where I expected them to (browser window).
I figured that standard out was the browser (httpServletResponse). Where am I going wrong here?
Basically, I have a class that connects to a database (call it db) and does queries/updates. I have a class (call it employee) that uses the db class. I have a jsp page that instantiates the employee class and executes method calls. The code in the db class that outputs SQL error messages (db class instantiated by employee class) never gets put in the browser window. Nor in the server log, nor the console.
How can I get system.out calls in classes db and employee to get output to the browser? The JSP outputs all other code and is not freezing nor not flushing the buffer.
Thanks!

I also use an Iplanet over which I have little control. But I can log on via telnet. If I log on (I use Reflection) and run my pages, the errors show in the Reflection window. If you have telnet access to the server, you might want to give this a try.
Another alternative would be to add a few lines to your classes that allow you to pass a reference to the jsp StringWriter from your jsp and use that to output the errors to the browser.

System.out.println capture to buffer

Hi All,
My application runs other application in back. How can I capture system.out.println() written by another application & display via dialog box.
Like :execl() or execv() function in C runtime library. Where every printf() message printed to passed buffer.
Thank you,
Avin Patel

If i understand your question correctly, you should execute command for you help.html file. The system will run default browser.
such as:
void runBrowser(String file)
{String cmd = null;
     Process p;
          try {
               String os = System.getProperty("os.name");
               if (os != null && os.startsWith("Windows")) {
                    if (os.startsWith("Windows 9") || os.startsWith("Windows Me"))
                    // Windows 9x/Me
                         cmd = "start " + file;
else
                    // Windows NT/2000/XP
                         cmd = "cmd /c start " + file;
p = Runtime.getRuntime().exec(cmd);
catch(IOException x)
// couldn't exec browser
System.err.println("Could not invoke browser, command=" + cmd);
}

Turn off System.out.println

The nohup.out file is getting too big, how to turn off System.out.println without change any coding?


java weblogic.Server > server.out 2>&1
 cheers
 mbg
 "Jen " <[email protected]> wrote in message
 news:[email protected]..
 >
 > How can I capture the System.out on windows?Thanks
 >
 > "Deyan D. Bektchiev" <[email protected]> wrote:
 > >just put the output to /dev/null on Unix/Linux or "nul" on Windows...
 > >
 > >Of course then the output is lost forever and you'll only have the
 > >Weblogic log files to look at any potential problems.
 > >
 > >--dejan
 > >
 > >java guy wrote:
 > >
 > >>The nohup.out file is getting too big, how to turn off
 System.out.println
 > >without change any coding?
 > >>
 > >>
 > >
 >

How to deal with the mouse events when the thread is running

Hi everybody,
I have a problem with my program.
Now I want to present a picture for some time in the Canvas,then automatically clear the screen, but when the user press the mousebutton or keybutton, I want to stop the thread and clear the screen.
How can I receive the mouse event when the thread is running?
Thanks,

I use my code in a GUI applet.
I try to use the code tag, it's the first time.
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//                    Thread.sleep(showtime);
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               if(pos==null){
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Redirecting System.out to a JTextArea

How can I redirect the System.out Stream into a JTextArea?
I found the method System.setOut(PrintStream out) but I don't know
how to get the PrintStream of my TextArea.

I don't know if this is the most efficient way but it provides an example of using Pipes:
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class TextAreaStream extends JTextArea implements Runnable{
     private static final PipedOutputStream _pipeOut = new PipedOutputStream();
     static{
               System.setOut( new PrintStream(_pipeOut) );
     private InputStream _pipeIn;
private byte[] buffer = new byte[256];
     public TextAreaStream(){
          this(1,10);
     public TextAreaStream(int numRows, int numCols){
          super(numRows, numCols);
          Thread t = new Thread(this);
          t.setDaemon(true);
          t.start();
          try{
          pipeIn = new BufferedInputStream(new PipedInputStream(pipeOut));
          catch(IOException e){
               System.err.println("Error creating pipe: "+e);
     public void run(){
          while(true){
               try{
                    //blocks at read
                    int bytesRead = _pipeIn.read(buffer);
                    append(new String(buffer,0,bytesRead));
               catch(IOException e){
                    System.err.println(e);
     public static void main(String[] args){
          JFrame f = new JFrame();
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          JTextArea text = new TextAreaStream();
          text.setBorder(BorderFactory.createTitledBorder("System.out"));
          f.getContentPane().add(text);
          //Add an input component
          JPanel north = new JPanel(new FlowLayout(FlowLayout.LEFT));
          final JTextField field = new JTextField(25);
          north.add(field);
          north.add(new JLabel("Add text, press Enter"));
          f.getContentPane().add(north, BorderLayout.NORTH);
          field.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent e){
                    System.out.println(field.getText());
                    field.setText("");
f.setSize(600, 400);
          f.show();
}

How to make add the program system.out messages to a applet text field?

How to make add the program system.out messages to a applet text field?
System.out.println("I wanna displany this message on a applet text field, thanks");

You may wish to change the output destination to a JTextArea. Please have a look at this link that likely shows what you want:
[http://forums.sun.com/thread.jspa?forumID=54&threadID=640376|http://forums.sun.com/thread.jspa?forumID=54&threadID=640376]
If you need other examples, search the forum. I found the search terms -- redirect system out textarea -- very helpful.
Good luck

How JTextArea may receive System.out events?

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