Re: System.out PrintWriter print() and flush() not flushing?

From:

Karsten Wutzke <kwutzke@web.de>

Newsgroups:

comp.lang.java.help

Date:

Fri, 29 Feb 2008 00:03:39 -0800 (PST)

Message-ID:

<267c1137-40da-4cac-b1dd-d179dd93e7ce@c33g2000hsd.googlegroups.com>

On 29 Feb., 06:23, Knute Johnson <nos...@rabbitbrush.frazmtn.com>
wrote:

Karsten Wutzke wrote:

On 29 Feb., 05:54, Knute Johnson <nos...@rabbitbrush.frazmtn.com>
wrote:

Karsten Wutzke wrote:

Hello!
I have a thread that listens to a server socket. When a message
arrives, I print it via
System.out.println("...");
While the program is listening and not receiving a message I simply
want to print one dot "." so the user can see the program is still
listening. However, the dots are not printed, they only appear after
another call to println(). I also call flush() after print but it
doesn't flush the buffer.
Does anyone know how to print only a dot without a newline? How?
Karsten

Are you trying to read from the console too? If that is the case I
think you will be unsuccessful.

From the docs for PrintWriter

"Unlike the PrintStream class, if automatic flushing is enabled it will
be done only when one of the println, printf, or format methods is
invoked, rather than whenever a newline character happens to be output.
These methods use the platform's own notion of line separator rather
than the newline character."

This could be part of the problem too. Maybe it would be better to use
PrintStream rather than PrintWriter.

--

Knute Johnson
email s/nospam/knute/

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Oops... I meant PrintStream from the beginning of my posting. So the
subject should read:

"System.out PrintStream print() and flush() not flushing?"

How do I go? Using

System.out.print(".");
System.out.flush();

Does not show the dot immediately as I'd like...

Karsten

I tried a simple program to do that and pause for a second and it works
fine on my XP computer. What OS are you using? Are you trying to do
input from the console too?

--

Knute Johnson
email s/nospam/knute/

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Could you post your simple program please?

I'm not getting any input from the console at any time. The software
is GUI driven.

It's strange.

Hmmm here's the code I use:

while ( sck.isConnected() )
{
    //flag raised when server delivers a null
    boolean wasNullBefore = false;

    try
    {
        String strMessage = br.readLine();

        if ( strMessage != null )
        {
            if ( wasNullBefore )
            {
                //last message was null, so a dot was printed,
                //make newline so non-null message is printed in a new
line
                System.out.println();
            }

            //message factory
            Message msg = mf.createIncomingMessage(strMessage);

            processIncomingMessage(msg);

            //lower flag
            wasNullBefore = false;
        }
        else
        {
            //if server delivers null print a dot (so not so many
lines get wasted)
            System.out.print(".");
            System.out.flush();

            //raise flag
            wasNullBefore = true;
        }

        Thread.sleep(250);
    }
    catch ( Exception e )
    {
        e.printStackTrace();
    }
}

Well I simply want to print dots on null messages so I don't waste a
whole line every 4th of a second... that's about it. But flush doesn't
flush. *shrug*

Karsten

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