I/O with external command

Hi,
I'm trying to run an external command inside my Java program and then
manage the I/O with that program with the console.

I paste the code

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;

public class RunExternalCommand {

    public static int runCommand(String command) {
        Process proc = null;
        try {
            proc = Runtime.getRuntime().exec(command);
            StreamGobbler outThread = new
StreamGobbler(proc.getInputStream(),
                    "OUT");
            StreamGobbler errThread = new
StreamGobbler(proc.getErrorStream(),
                    "ERR");
            StreamGobbler stdinThread = new StreamGobbler(System.in, proc
                    .getOutputStream(), "STDIN");

            stdinThread.start();
            outThread.start();
            errThread.start();

            proc.waitFor();
        } catch (IOException e) {
        } catch (InterruptedException e) {
        }
        return 0;
    }
}

class StreamGobbler extends Thread {
    InputStream is;
    PrintStream out;
    String type;

    StreamGobbler(InputStream is, String type) {
        this.is = is;
        this.out = System.out;
        this.type = type;
    }

    StreamGobbler(InputStream is, OutputStream os, String type) {
        this.is = is;
        this.out = new PrintStream(os);
        this.type = type;
    }

    public void run() {
        try {
            InputStreamReader isr = new InputStreamReader(is);

            int b = 0;
            while ((b = isr.read()) != -1) {
                out.print((char) b);
            }

        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }
}

I can run the external command (I see the output). However, when I have
to insert some input and then press Enter, the external command doesn't
get what I write and it's stuck waiting for input.

Any ideas?
Thanks