Clear the Screen

[Dave]

Hi,

I have done some research, trying to Clear The Screen in java code.

The first option was the obv:
system.out.prin t("\n\n\n\n\n\n \n\n\n\n\n\n");

then i heard about this method:
System.out.prin t((char)27 + "[2J");

However, it doen't work unless "ansi.sys" is loaded and very few WinXP
user's have this.

Any help appreciated in trying to solve this problem.

Cheers,
Dave

[Nathan Zumwalt]

It's kind of a hack, but what about this:

Runtime.exec("c ls");

This makes your application platform-dependent, but it looks like your
stated alternative does this as well.

-Nathan

"Dave" <bigdavepotnood le*SPAM*hotmail .com> wrote in message news:<3f******* *************** *@news-text.dial.pipex .com>...

Hi,

I have done some research, trying to Clear The Screen in java code.

The first option was the obv:
system.out.prin t("\n\n\n\n\n\n \n\n\n\n\n\n");

then i heard about this method:
System.out.prin t((char)27 + "[2J");

However, it doen't work unless "ansi.sys" is loaded and very few WinXP
user's have this.

Any help appreciated in trying to solve this problem.

Cheers,
Dave

[Denz]

Ive seen this question before- with no real solution.
Surely it wouldnt have been difficult to provide a clear screen, and even
basic screen cursor positioning?
It would make text-mode java alot more useful.

"Dave" <bigdavepotnood le*SPAM*hotmail .com> wrote in message
news:3f******** *************** @news-text.dial.pipex .com...

Hi,

I have done some research, trying to Clear The Screen in java code.

The first option was the obv:
system.out.prin t("\n\n\n\n\n\n \n\n\n\n\n\n");

then i heard about this method:
System.out.prin t((char)27 + "[2J");

However, it doen't work unless "ansi.sys" is loaded and very few WinXP
user's have this.

Any help appreciated in trying to solve this problem.

Cheers,
Dave

[Silvio Bierman]

"Dave" <bigdavepotnood le*SPAM*hotmail .com> wrote in message
news:3f******** *************** @news-text.dial.pipex .com...

Hi,

I have done some research, trying to Clear The Screen in java code.

The first option was the obv:
system.out.prin t("\n\n\n\n\n\n \n\n\n\n\n\n");

then i heard about this method:
System.out.prin t((char)27 + "[2J");

However, it doen't work unless "ansi.sys" is loaded and very few WinXP
user's have this.

Any help appreciated in trying to solve this problem.

Cheers,
Dave

Look at jcurses on sourceforge.

Silvio Bierman

[Christian]

Printing out the form-feed character will clear the screen

System.out.prin t("\f");

Hope this helps!

Christian

[Anthony Borla]

"Denz" <RU*****@RUBBIS Hhotmail.com> wrote in message
news:Kv******** *******@news-server.bigpond. net.au...

Ive seen this question before- with no real solution.
Surely it wouldnt have been difficult to provide a clear
screen, and even basic screen cursor positioning?

It would make text-mode java alot more useful.

Unfortunately these tasks are inherently operating system-specific, and
cannot be implemented in any standard way across platforms. Some platforms,
in fact, don't even understand the concepts of 'screen', or 'cursor', so
wouldn't even have any use for classes that implemented these abstractions.
Even the 'standard' C and C++ languages which, like Java, aim for platform
independance, do not implement such functionality.

System-specific tasks such as these may be performed via:

* 'Runtime.getRun time().exec(... )'

* Writing Java Native Interface [JNI] routines which tap into
the relevant operating system functionality

The first option should really be seen as a 'quick and dirty' approach - it
allows you to perform certain system-specific tasks but with very little
control. A program, to be considered robust, would make no more than sparing
use of this facility. If you find you are relying on it heavily you may need
to seriously question whether Java is the ideal development tool for this
task [a scripting language (Perl, Python) might be more suitable ?], or more
of a development commitment needs be made by using JNI.

There is nothing inherently wrong with JNI except that its use helps defeat
one of Java's most important qualities - platform independance - and it
introduces 'weaknesses' into the application because program execution
occurs outside the control of the JVM, and any failure here could be
catastrophic. On the flipside, Java would be a very limited development
environment without it since it allows for the tapping into system-specific
functionality in a controlled, and efficient way.

So, to provide the facilities you seek, you need to implement suitable JNI
routines. Again, options are available:

* Tap into someone else's work. As another respondant has
already meantioned, the JCurses package provides a
reasonable suit of screen handling routines for the *NIX
and Windows-familiy platforms

* Write your own. This isn't as difficult as you might imagine,
and might be the best approach if all you require is a
few simple routines like:

- Clearing the screen
- Moving the cursor to specified positions
- Accepting input [say a single keystroke] without pressing
ENTER

A good start would be the JNI tutorial at the Sun site, and,
of course, perusal of the documentation for the system
functions implementing this functionality

Anyway, apologies for the longwindedness of the response. Hopefully, though,
some useful insights have been provided.

Cheers,

Anthony Borla

[Anthony Borla]

"Christian" <ja******@email user.net> wrote in message
news:32******** *************** ***@posting.goo gle.com...

Printing out the form-feed character will clear the screen

System.out.prin t("\f");

Hope this helps!

Sadly, it doesn't do as you expect - it's behaviour various with the
platform. Nice try, though :)

Cheers,

Anthony Borla

[Anthony Borla]

"Nathan Zumwalt" <na*****@hotmai l.com> wrote in message
news:52******** *************** ***@posting.goo gle.com...

It's kind of a hack, but what about this:

Runtime.exec("c ls");

This makes your application platform-dependent, but it looks
like your stated alternative does this as well.

Actually, this won't work. Yes, the 'cls' command is invoked, *but* it is
invoked in a new process ['command.com' or 'cmd.exe' is exected creating a
new process], and *does not* clear the Java application's console.

Cheers,

Anthony Borla

[nos]

But if they can implement "beep", and they do,
they should be able to implement "cls" too.

"Anthony Borla" <aj*****@bigpon d.com> wrote in message
news:g0******** ********@news-server.bigpond. net.au...

"Denz" <RU*****@RUBBIS Hhotmail.com> wrote in message
news:Kv******** *******@news-server.bigpond. net.au...

Ive seen this question before- with no real solution.
Surely it wouldnt have been difficult to provide a clear
screen, and even basic screen cursor positioning?

It would make text-mode java alot more useful.

Unfortunately these tasks are inherently operating system-specific, and
cannot be implemented in any standard way across platforms. Some

platforms, in fact, don't even understand the concepts of 'screen', or 'cursor', so
wouldn't even have any use for classes that implemented these abstractions. Even the 'standard' C and C++ languages which, like Java, aim for platform
independance, do not implement such functionality.

System-specific tasks such as these may be performed via:

* 'Runtime.getRun time().exec(... )'

* Writing Java Native Interface [JNI] routines which tap into
the relevant operating system functionality

The first option should really be seen as a 'quick and dirty' approach - it allows you to perform certain system-specific tasks but with very little
control. A program, to be considered robust, would make no more than sparing use of this facility. If you find you are relying on it heavily you may need to seriously question whether Java is the ideal development tool for this
task [a scripting language (Perl, Python) might be more suitable ?], or more of a development commitment needs be made by using JNI.

There is nothing inherently wrong with JNI except that its use helps defeat one of Java's most important qualities - platform independance - and it
introduces 'weaknesses' into the application because program execution
occurs outside the control of the JVM, and any failure here could be
catastrophic. On the flipside, Java would be a very limited development
environment without it since it allows for the tapping into system-specific functionality in a controlled, and efficient way.

So, to provide the facilities you seek, you need to implement suitable JNI
routines. Again, options are available:

* Tap into someone else's work. As another respondant has
already meantioned, the JCurses package provides a
reasonable suit of screen handling routines for the *NIX
and Windows-familiy platforms

* Write your own. This isn't as difficult as you might imagine,
and might be the best approach if all you require is a
few simple routines like:

- Clearing the screen
- Moving the cursor to specified positions
- Accepting input [say a single keystroke] without pressing
ENTER

A good start would be the JNI tutorial at the Sun site, and,
of course, perusal of the documentation for the system
functions implementing this functionality

Anyway, apologies for the longwindedness of the response. Hopefully, though, some useful insights have been provided.

Cheers,

Anthony Borla

[Stewart Gordon]

While it was 9/1/04 3:04 pm throughout the UK, nos sprinkled little
black dots on a white screen, and they fell thus:

But if they can implement "beep", and they do,
they should be able to implement "cls" too.

<snip top of upside-down reply>

That's because BEL is a standard ASCII character (code 7) and it's
pretty much standard that any terminal/console would render it by
beeping. OTOH, for some reason I can't imagine FF (12) doesn't
standardly mean clear screen, and nor does any other ASCII string.

But I agree that having a portable means of screen clearing would be
handy. BTW, have the rest of you people stopped telling people to try
what you can't be bothered to try for yourself?

Stewart.

--
My e-mail is valid but not my primary mailbox, aside from its being the
unfortunate victim of intensive mail-bombing at the moment. Please keep
replies on the 'group where everyone may benefit.