Open a new command prompt and send commands from a Java program running in a command prompt

I have a Java program running in a command prompt (A) and would like to open a new command prompt (B), run some commands in B, and then close the B command prompt window.

I have been using these posts as reference:

Create a new cmd.exe window from within another cmd.exe prompt

How to open a command prompt and input different commands from a java program

I was able to open a command prompt from my Java program, How to run some exe in this command prompt using java code?

pass multiple parameters to ProcessBuilder with a space

Start CMD by using ProcessBuilder

Here is my code:

public static void startCMD(String appName) {
        // init shell       
        String[] cmd = new String[]{"cmd.exe", "/C", "start"};      
        ProcessBuilder builder = new ProcessBuilder(cmd);
        Process p = null;
        try {
            p = builder.start();
        } catch (IOException e) {
            System.out.println(e);
        }
        // get stdin of shell
        BufferedWriter p_stdin = new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));

        // execute the desired command (here: ls) n times
        try {
            // single execution
            p_stdin.write("C:");
            p_stdin.newLine();
            p_stdin.flush();

            p_stdin.write("cd C:\\" + appName);
            p_stdin.newLine();
            p_stdin.flush();

            p_stdin.write("sbt \"run 8080\"");
            p_stdin.newLine();
            p_stdin.flush();

        } catch (IOException e) {
            System.out.println(e);
        }

        // finally close the shell by execution exit command
        try {
            p_stdin.write("exit");
            p_stdin.newLine();
            p_stdin.flush();
        } catch (IOException e) {
            System.out.println(e);
        }

        // write stdout of shell (=output of all commands)
        Scanner s = new Scanner(p.getInputStream());
        while (s.hasNext()) {
            System.out.println(s.next());
        }
        s.close();
    }

The code above opens a new command prompt (B), but none of the commands are entered in this new command prompt (B). The current Java program just hangs in the command prompt (A).

I know I am missing some commands and parameters to have the command prompt (B) to close when the process is finished.

Is there a better way to build this?

I appreciate the help.