Runtime.getRuntime().exec(java test)

Question

Hi,
As part of a thesis for college, I am trying to execute a test java program. The program executes okay and I can read the results okay.
Sample code.
process = Runtime.getRuntime().exec("java test");
InputStream iOutStream = process.getInputStream();
InputStream ErrorStream = process.getErrorStream();
However, I need to be able to execute a progam that reads a parameter from the screen. I tried to pass a parameter file but it doesn't work.
process = Runtime.getRuntime().exec("java test <input.txt");
I also tried just passing the parameters as a string array but it doesn't work either.
process = Runtime.getRuntime().exec("java test 2, 2");
Is there any other way that I can get the process to accept parameters?
My deadline is looming so any help would be greatly appreciated.
Thanks
Eleanor
[email protected]

Answer 1

I think you are waiting when reading the output before you write to the stream until it becomes NULL or -1. That will never finish if the program you execute is expecting input!
See a working example:
This class does nothing than print a line on the console, then waits for a line of input, then prints the result again on the console. This is the class you'd execute from some other java code:
import java.io.*;
public class Input {
    public static void main(String args[]) {
        try {
            System.out.println("Before input");
            BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
            String s=r.readLine();
            System.out.println("Got line : " + s);
        } catch(Exception e) {
                System.out.println(e.getMessage());
}The following 'controls' the input-test class above, so compile the classes and execute the following one:
import java.io.*;
import java.lang.*;
public class test {
    public static void main(String args[]) {
        try {
            Process p = Runtime.getRuntime().exec("java Input");
            BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
            BufferedWriter w = new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));
            String s=r.readLine(); // You cannot read until NULL because that will not happen before you have 'input' something
            System.out.println("Got: " + s);
            w.write("cvxcvxcvx\n\r");
            w.flush();
            System.out.println("waiting result:");
            while( (s=r.readLine()) != null) { // read until finished.
                System.out.println("after : " + s);
        } catch(Exception e) {
                System.out.println(e.getMessage());               
}