Inputting data into an external app from Java

Lawrene

I use this standard code to capture and display the output from an application in a JTextArea called outputTextServer1. The error checking has been removed. Works fine.

Process proc = null;
ProcessBuilder builder=null;
builder = new ProcessBuilder("java","-jar", "test.jar");                        
proc = builder.start();
Thread outputGobbler = new Thread(new StreamGobbler(proc.getInputStream(),  outputTextServer1));
outputGobbler.start();

I now want the user to be able to enter a command into a JTextField and for this to be sent back to the app. It is a complied app which can't be changed. I have read many variants using pipes, System.out and redirect but as far as I understand, none of these methods do this.The contents of the app can't be changed. How can this be done? (Can this be done?)

Thanks in advance.