Process process = Runtime.getRuntime().exec("su", null,null);
            OutputStream outputStream = process.getOutputStream();
            outputStream.write(("/proc/net/arp -a").getBytes("ASCII"));
            outputStream.flush();
            outputStream.close();
           //process.waitFor();
    
        BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        StringBuilder builder = new StringBuilder();
        String line = null;
        while ( (line = reader.readLine()) != null) {
            builder.append(line);
            builder.append(System.getProperty("line.separator"));
        }
        String result = builder.toString();
        System.out.println(result);

As mentioned in the title I am trying to basically get the arp table. Since I was getting permission denied directly with arp -a, I added su (yes, I have root permission on my device).
Now I fixed the permission denied error but however I don’t get any output from the process. Why?
On desktop machines I have always did this.