Jalankan File Executable di java

private String Jalankan(String perintah) throws IOException {
       Process p = Runtime.getRuntime().exec(perintah);
       InputStream stdoutStream = new BufferedInputStream(p.getInputStream());

       StringBuffer buffer= new StringBuffer();
       for (;;) {
               int c = stdoutStream.read();
               if (c == -1) break;
               buffer.append((char)c);
       }
       String outputText = buffer.toString();

       stdoutStream.close();

       return outputText;
   }