Running Java programs through a GUI

Question

Hi All.
I have a Java GUI which compiles and runs other Java programs through the use of JButtons.
The user clicks one button to compile and another to run. Compile is running fine but Run is slightly odd.
When I click the Run button the Java program does not run until I minimize the GUI or switch to another window or application.
So for example I click the Run button, nothing happens, I then alt+tab or minimize to say NetBeans (which I am using to develop it) or an IE window. The program then runs successfully
My method for running the program is:
public void clickRunProgram() {
        try {
            Runtime r = Runtime.getRuntime();
            r.exec("cmd /c java Testing");
        catch (IOException ex) {
            Logger.getLogger(ProgrammingEnvironmentGUI.class.getName()).log(Level.SEVERE, null, ex);
    }Any ideas?
Cheers.
Edited by: lobrien9 on 25-Mar-2008 12:57

Answer 1

You must give the process its input and get its output or it won't run. Try something like this:
        // create the process to test
        Process acm = Runtime.getRuntime().exec("cmd /c java Testing");
        // send input
        PrintWriter processOut = new PrintWriter(acm.getOutputStream());
        processOut.print("input");
        processOut.flush();
        processOut.close();
        // get output
        StringBuilder givenOutputBuilder = new StringBuilder();
        BufferedReader processIn = new BufferedReader(
                new InputStreamReader(acm.getInputStream()));
        String line = processIn.readLine();
        while (line != null) {
            givenOutputBuilder.append(line + "\n");
            line = processIn.readLine();
        }