Question

I want to fire a command line executible with the parameters entered in GUI.

Process class can be used to fork my required command line process from the Java application, and I used the getInputStream() method of Process object to get the result and got it displayed in the GUI.

private void confirmActionPerformed(java.awt.event.ActionEvent evt) {                                       
    String output;
    try {
        Process p = Runtime.getRuntime().exec("my command line exe with parameters");
        BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));

        while ((output = stdInput.readLine()) != null) {
            TextField.setText(TextField.getText()+output+"\n");
        }
    } catch (IOException e) {
        System.out.println("Exception in Process");
        e.printStackTrace();
    }
}   

This is my code which is an event listener of a button pressed event and I attempted to display the result of the process in the text field (java swing component).

This process actually runs for quite a long time and shows some statistics as and when it runs when run in command line, but when i attempt it in GUI with the above code I’m getting the entire consolidated result only after the process finish running. I’m not getting the TextField updated as and when it is executing.

What would be the cause of this issue?

Answer 1

This is because the whole thing is done by the Swing event-handling thread.

Perhaps should you consider creating a separate thread and update the TextField with a SwingUtilities.invokeLater().