Writing to InputStream of a Java Process

The Process OutputStream (our point of view) is the STDIN from the process point of view

OutputStream stdin = process.getOutputStream(); // write to this

So what you have should be correct.

My driver (apply your own best practices with try-with-resources statements)

public class ProcessWriter {
    public static void main(String[] args) throws Exception {
        ProcessBuilder builder = new ProcessBuilder("java", "Test");
        builder.directory(new File("C:\\Users\\sotirios.delimanolis\\Downloads"));
        Process process = builder.start();

        OutputStream stdin = process.getOutputStream(); // <- Eh?
        InputStream stdout = process.getInputStream();

        BufferedReader reader = new BufferedReader(new InputStreamReader(stdout));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(stdin));

        writer.write("Sup buddy");
        writer.flush();
        writer.close();

        Scanner scanner = new Scanner(stdout);
        while (scanner.hasNextLine()) {
            System.out.println(scanner.nextLine());
        }
    }
}

My application

public class Test {

    public static void main(String[] args) throws Exception {
        Scanner console = new Scanner(System.in);
        System.out.println("heello World");
        while(console.hasNextLine()) {
            System.out.println(console.nextLine());
        }
    }
}

Running the driver prints

heello World
Sup buddy

For some reason I need the close(). The flush() alone won’t do it.

Edit It also works if instead of the close() you provide a \n.

So with

writer.write("Sup buddy");
writer.write("\n");
writer.write("this is more\n");
writer.flush();    

the driver prints

heello World
Sup buddy
this is more