Java-在程序仍在运行时使用exec并读取输出

Question

So I'm creating a gui for an exe in Java. Bit cumbersome but I'm trying. Due to this program being a console program, I need to read the output of the program while it's running and put that into a Swing textbox. But every way I've tried it is either unstable or simply does not work at all. Could anyone help me out with this? Note I have tried Apache Commons exec with little success. Also I'm trying to make this cross-platform and have created a method for getting the OS:

public enum OSType {
    WINDOWS, OSX, LINUX, DAFUQ
}

/**
 * Gets OS running on then caches result
 * @return OS running on
 **/
public static OSType getOS() {
    if (os != null)
        return os;
    else {
        os = getOperatingSystem();
        return os;
    }
}

/** Don't use this! Use {@link Frame#getOS()} instead **/
public static OSType getOperatingSystem() {
    String OS = System.getProperty("os.name").toLowerCase();
    if (OS.indexOf("win") >= 0)
        return OSType.WINDOWS;
    else if (OS.indexOf("mac") >= 0)
        return OSType.OSX;
    else if (OS.indexOf("nix") >= 0 || OS.indexOf("nux") >= 0 || OS.indexOf("aix") > 0)
        return OSType.LINUX;
    else
        return OSType.DAFUQ;
}

EDIT:

To clarify, I am creating a .jar program that acts as a gui for a EXE. This is the code that I am currently trying to use to start the program:

ProcessBuilder prc = new ProcessBuilder(commands);

        prc.redirectErrorStream(true);

        try {
            Frame.exec = prc.start();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

The commands variable is just a list for the commands I need to execute. The program is running correctly because I can see it working on the task manager. Here is also the code for how I am reading from the InputStream of the process:

BufferedReader in = new BufferedReader(new InputStreamReader(exec.getInputStream()));
        String line;
        while ((line = in.readLine()) != null) {
            System.out.println(line);
        }

I am trying to read from the stream asynchronously, so this code is in another thread, which is why I needed to store the "exec" variable.

Answer 1

I've tried to get from ProcessBuilder but it waits until the the program is closed before it can read the console output.

No it doesn't. It reads whatever is written as soon as it's written. What you're seeing is the effect of buffering output in the child process, probably by stdio . If you're not in control of the code of that process there is nothing you can do about it.