Java Process with Input/Output Stream

I have the following code example below. Whereby you can enter a command to the bash shell i.e. echo test and have the result echo'd back. However, after the first read. Other output streams don't work?

Why is this or am I doing something wrong? My end goal is to created a Threaded scheduled task that executes a command periodically to /bash so the OutputStream and InputStream would have to work in tandem and not stop working. I have also been experiencing the error java.io.IOException: Broken pipe any ideas?

Thanks.

String line;
Scanner scan = new Scanner(System.in);

Process process = Runtime.getRuntime ().exec ("/bin/bash");
OutputStream stdin = process.getOutputStream ();
InputStream stderr = process.getErrorStream ();
InputStream stdout = process.getInputStream ();

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

String input = scan.nextLine();
input += "\n";
writer.write(input);
writer.flush();

input = scan.nextLine();
input += "\n";
writer.write(input);
writer.flush();

while ((line = reader.readLine ()) != null) {
System.out.println ("Stdout: " + line);
}

input = scan.nextLine();
input += "\n";
writer.write(input);
writer.close();

while ((line = reader.readLine ()) != null) {
System.out.println ("Stdout: " + line);
}