How to write to System.in?

No. It's a shell thing. For a demo, here are two simple programs:

import java.io.*;

public class Reading {

public static void main(String[] args) throws IOException {

BufferedReader in = new BufferedReader(new InputStreamReader(System.in));

String line;

while ((line = in.readLine()) != null)

System.out.format("Reading sees [%s]%n", line);

}

}

and

public class Writing {

public static void main(String[] args) {

for (int i = 0; i < 10; ++i)

System.out.format("This is line %d%n", i);

}

}

Once compiled, you run them from the command line by:

% java Writing | java Reading

... or however you shell expressed piping the output from one process to be the input of another.

Try that!

Hippolytea at 2007-7-12 14:44:02 >

Hunter is right, too. You could first redirect the writer's output to a file:

$java Writing > w.txt

Then run the reader using that input:

$java Reading < w.txt

Sometimes this doesn't work -- say the programs have to run for a long time, and

then you'll have to run them concurrently, with the pipe.

UNIX guys do this all the time.

Hippolytea at 2007-7-12 14:44:02 >

Try something like this (Running on WinXP w/ Cygwin, via bash):

Test.java:

import java.io.*;

import java.util.*;

public class Test{

public static void main(String[] args) {

System.out.print("Type 'ok' to continue: ");

Scanner scanner = new Scanner(System.in);

String next = scanner.next();

if (next.equals("ok")) {

System.out.println("\n Yay...");

} else {

System.out.println("\n Oh poo...");

}

}

}

test.txt (Just the text "ok" with a newline following):

ok

test2.txt (Just the text "boo" with a newline following):

boo

kevin.wallace@MOKANSASC2DA77 ~/java$ java Test < test.txt

Type 'ok' to continue:

Yay...

kevin.wallace@MOKANSASC2DA77 ~/java$ java Test < test2.txt

Type 'ok' to continue:

Oh poo...

I don't know what the equivalent without Cygwin's bash shell would look like.

kevjavaa at 2007-7-12 14:44:02 >

> Guys, I am trying to Drive my console application

> using JUnit. It should be able to punch in text

> dynamically.

Maybe if you passed in your InputStream object to the console app part, and used a driver to instantiate it (I haven't tested this)...

public class Myapp {

InputStream in = null;

public Myapp() {

this.in = System.in;

doConsoleThing();

}

public Myapp(InputStream in) {

this.in = in;

doConsoleThing();

}

public static void main(String[] args) {

Myapp app = new Myapp();

}

public void doConsoleThing() {

// Do your nifty console thing...

}

Your JUnit test would do something like:

public void testMyapp() {

FileInputStream fis = new FileInputStream( new File("test.txt") );

Myapp app = new Myapp(fis);

}

kevjavaa at 2007-7-21 21:28:24 >