code: public static void main(String[] args) throws Exception {
      if (args.length != 1) {
        System.err.println("Usage:  ListPeople ADDRESS_BOOK_FILE");
        System.exit(-1);
      }
  
      // Read the existing address book.
      AddressBook addressBook =
        AddressBook.parseFrom(new FileInputStream(args[0]));
  
      Print(addressBook);
    }
docs: the information inside.