qualcosa del genere?
codice:
public static void execDir() {
        File f = new File("C:/Users/Andrea/Desktop/dir_result.txt");
        Runtime r = Runtime.getRuntime();
        try {
            String cmd = "cmd /c dir C:\\Windows";
            Process proc = r.exec(cmd);
            
            BufferedReader br = new BufferedReader(new InputStreamReader(proc.getInputStream()));
            BufferedWriter bw = new BufferedWriter(new FileWriter(f));           
            
            
            String line = "";
            while ((line = br.readLine())!= null) {                
                bw.write(line+"\r\n");
            }
            bw.flush();
            bw.close();
            br.close();
            proc.destroy();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        
    }