Programatically interact with an I/O program in Java

Question

I am writing a program that utilizes a third party mathematics software, "Maxima". This program is a command line interface, and so it can communicate through my Java program with simple I/O routing. I have already figured out how to run the program from within Java, and I have read a lot about how I can reconfigure System.out and how InputStreams/OutputStreams work, but I can't figure out how to do the following (what I think should be a pretty simple task):

1. Output to Maxima a command from Java, (like the string "5 + 5;")
2. Retrieve Maxima's output, and deal with it from Java code (like maybe printing the given string + "blah").
3. Output another command to Maxima from Java...
4. etc.

- Below is code which will run Maxima and allow me to interact with it on the Eclipse Console

public static void main(final String[] args) {

    // An idea I had for manipulaing how the printstream works.
    // Set the system.out to be a custom Prinstream.
    // final PrintStream interceptor = new Interceptor(origOut);
    // System.setOut(interceptor);

    // Run the program:
    final String programLocation = "\"C:\\Program Files (x86)\\Maxima-sbcl-5.37.2\\bin\\maxima.bat\"";
    final ProcessBuilder pb = new ProcessBuilder();
    pb.redirectInput(Redirect.INHERIT); // Inherit I/O
    pb.redirectOutput(Redirect.INHERIT);
    pb.command(programLocation);

    try {
        // Start the program and allow it to run in Eclipse's/the program's
        // console.
        pb.start().waitFor();
    } catch (final InterruptedException e) {
        e.printStackTrace();
    } catch (final IOException e) {
        e.printStackTrace();
    }

}

This allows for the following style of interaction:

Answer 1

Thanks to the words of wisdom from @RealSkeptic, I think I worked out a solution here.

The key was building a BufferedWriter, and a BufferedReader to interact with the I/O of Maxima. That is:

BufferedWriter w = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
BufferedReader r = new BufferedReader(new InputStreamReader(process.getInputStream()));

Those two lines of code create buffered readers and writers which can input data to Maxima, and read what Maxima output. Here is a (fairly lengthy) use case of this method, which I use to do basically what I asked in the question:

public class TestClass {

public static void main(final String[] args) {
    @SuppressWarnings("unused")
    final TestClass ts = new TestClass();
}

private BufferedWriter w;
private BufferedReader r;

public TestClass() {
    // Start the process using process builder
    final String programLocation = "\"C:\\Program Files (x86)\\Maxima-sbcl-5.37.2\\bin\\maxima.bat\"";
    final ProcessBuilder pb = new ProcessBuilder();
    pb.command(programLocation);
    Process process;
    try {
        process = pb.start();
    } catch (final IOException e) {
        e.printStackTrace();
        process = null;
        // killProgram();
    }

    // Build your own wrappers for communicating with the program.
    w = new BufferedWriter(
            new OutputStreamWriter(process.getOutputStream()));
    r = new BufferedReader(new InputStreamReader(process.getInputStream()));

    // Print the five starting messages.
    printFromBuffer();
    printFromBuffer();
    printFromBuffer();
    printFromBuffer();
    printFromBuffer();

    // Run the following three commands in Maxima
    runCommand("5+5;");
    runCommand("2*65;");
    runCommand("quit();");
}

/**
 * Runs the given string and prints out the returned answer.
 */
private void runCommand(final String s) {
    try {
        w.write(s);
        w.flush();
        printFromBuffer();
        printFromBuffer();
    } catch (final IOException e) {
        e.printStackTrace();
    }
}

private void printFromBuffer() {
    try {
        final String s = r.readLine();

        System.out.println(s + " -blah");

    } catch (final IOException e) {
        System.err.println(e.getMessage());
        e.printStackTrace();
    }
}
}