Designation standard output as File type

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Alan - 30 Nov 2007 01:30 GMT

I have a method (fragment below) that takes a File type "outFile"
as the output file. However, if the user of this method specifies
"null" for that parameter, I want to make the output go to standard
output instead of a file.

My question: To what do I set outFile (File type) to make the
output go to standard output (display)? System.out is of a type
PrintStream.

Thanks, Alan

public static void printData(File dir, File outFile)
{
try
{
if (outFile == null)
{
outFile = ?????; // Default is standard output (System.out)
}
. . .

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Stefan Ram - 30 Nov 2007 01:39 GMT

>My question: To what do I set outFile (File type) to make the
>output go to standard output (display)?

If you use »File« to refer to »java.io.File«,
there is no portable way to do this.

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Andrew Thompson - 30 Nov 2007 01:42 GMT

>I have a method (fragment below) that takes a File type "outFile"
>as the output file. ...System.out is of a type
>PrintStream.

...

>public static void printData(File dir, File outFile)

This is probably better specified as

public static void printData(InputStream is, OuputStream os)

Then it might be called in code (something) like this..

// redirect the streams
printData( new FileInputStream(dir), System.out );

As an aside. Why is your initial 'File' parameter called
'dir'? That suggests a directory to me.

Signature

Andrew Thompson
http://www.physci.org/

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Alan - 30 Nov 2007 01:49 GMT

I am traversing subdirectories and processing certain types of
files found. So, I test dir to see if it is a directory or a file
(both of type File).

Alan

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Roedy Green - 30 Nov 2007 08:31 GMT

On Thu, 29 Nov 2007 17:30:38 -0800 (PST), Alan
<jalanthomas@verizon.net> wrote, quoted or indirectly quoted someone
who said :

> I have a method (fragment below) that takes a File type "outFile"
>as the output file. However, if the user of this method specifies
>"null" for that parameter, I want to make the output go to standard
>output instead of a file.

See if this works:

final PrintStream ps;

if ( f == null )
{
ps = System.out;
}
else
{
ps = new PrintStream ( new File(f) );
}

final PrintWriter pw = new PrintWriter( ps );

Signature

Roedy Green Canadian Mind Products
The Java Glossary
http://mindprod.com

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Mark Rafn - 30 Nov 2007 21:24 GMT

> My question: To what do I set outFile (File type) to make the
>output go to standard output (display)? System.out is of a type
>PrintStream.

Right. The first line of javadoc for java.io.File makes this clear: "An
abstract representation of file and directory pathnames."

stdout is not a path name. It's an output stream.

>public static void printData(File dir, File outFile)

You'll need to write a printData method that takes an OutputStream (or better,
a Writer). There is no path for stdout, so there is no File object that
represents it.
--
Mark Rafn dagon@dagon.net <http://www.dagon.net/>

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Designation standard output as File type

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