How to give input to a Java program which is fed as input to another Java Program using Runtime.getRuntime.exec()?

Here is the code. It is taking SampleProg.java as input. I am unable to provide the input for SampleProg.java. What I am looking for is to compile, run and give input for test cases for the program. I tried using Buffered Writer but I am unable to write into the input program.
It is getting stuck while giving input. How can i provide the input. I am getting stuck at the part where i am giving input and it is not processing further. I also tried to use ProcessBuilder, but i was stuck with the same issue.

CODE: Example.java

    public class Example {
    
        public static void main(String[] args) {
            try{
                String path = "src/main/java/SampleProg.java";
                compile(pathJava);
                Process runProcess = run();
                runProcess.waitFor();
                BufferedReader in = new BufferedReader(new 
                InputStreamReader(runProcess.getInputStream()));
                String s;
                Scanner sc = new Scanner(System.in);
                while((s = in.readLine()) != null){
                    System.out.println(s);
                    op.write(sc.nextInt());
                    op.close();
                      }
                    }
                catch(Exception e){
                e.printStackTrace();
                 }
               }
            private static void compile(String pathJava) throws 
            IOException, InterruptedException {
            String [] cmd = new String[4];
            cmd[0] = "javac";
            cmd[1] = "-d";
            cmd[2] = ".";
            cmd[3] = pathJava;
            Runtime r = Runtime.getRuntime();
            Process compileProcess = r.exec(cmd);
            compileProcess.waitFor();
            }
        
            private static Process run() throws IOException {
            String [] cmd = new String[2];
            cmd[0] = "java";
            cmd[1] = "SampleProg";
            Runtime r = Runtime.getRuntime();
            return r.exec(cmd);
          }
          }