content: // See README.txt for information and build instructions.
  
  import com.example.tutorial.AddressBookProtos.AddressBook;
  import com.example.tutorial.AddressBookProtos.Person;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.PrintStream;
  
  class ListPeople {
    // Iterates though all people in the AddressBook and prints info about them.
    static void Print(AddressBook addressBook) {
      for (Person person: addressBook.getPeopleList()) {
        System.out.println("Person ID: " + person.getId());
        System.out.println("  Name: " + person.getName());
        if (!person.getEmail().isEmpty()) {
          System.out.println("  E-mail address: " + person.getEmail());
        }
  
        for (Person.PhoneNumber phoneNumber : person.getPhonesList()) {
          switch (phoneNumber.getType()) {
            case MOBILE:
              System.out.print("  Mobile phone #: ");
              break;
            case HOME:
              System.out.print("  Home phone #: ");
              break;
            case WORK:
              System.out.print("  Work phone #: ");
              break;
            default:
              System.out.println(" Unknown phone #: ");
              break;
          }
          System.out.println(phoneNumber.getNumber());
        }
      }
    }
  
    // Main function:  Reads the entire address book from a file and prints all
    //   the information inside.
    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);
    }
  }
  