Read data, add it to a list and then print it

Question

I have to create a class Agenda, and then create a list of schedules and print.

Man main:

public static void main(String[] args) {
    List<Agenda> lista = new ArrayList<Agenda>();
    Agenda agenda = new Agenda();
    Scanner scanner = new Scanner(System.in);

    System.out.println("Digite o nome");
    agenda.setNome(scanner.next()); 

    System.out.println("Deseja digitar outro ? ");
    String resp = scanner.next();

    while(resp.equalsIgnoreCase("Y")) {
        System.out.println("Digite o nome");
        agenda.setNome(scanner.next());
    }

    lista.add(agenda);
    System.out.println(lista);
}

This way, if the user typed more than 2 contacts, would appear only the last.

I’m trying to think of a solution, but I couldn’t imagine anything to solve (print all the contacts typed).

Answer 1

Within the while you are changing the same instance of Agenda (is not creating a new one, which I understood to be the intention). Moreover, if resp for "Y", he will go into loop infinite, for resp is not updated within the while, then its value will remain "Y" and he’ll never get out of this loop.

If resp is not "Y", he doesn’t get into the while and you add the agenda to the list (only one). Then the first thing is to fix this loop forever read a new value from resp (to know whether or not to continue reading more data), and always create a new schedule to add to the list (instead of changing the same).

So first let’s change the class Agenda, adding a constructor named:

public class Agenda {
    private String nome;

    public Agenda(String nome) {
        this.nome = nome;
    }

    public String getNome() {
        return this.nome;
    }
}

I’m assuming it only makes sense to create an agenda if it has a name. So there’s no reason to have a constructor with no parameters, which creates an unnamed directory. Just create builders that make sense. I also removed the Setter because there seems to be no use for it (unless there is some rule that determines that an agenda can change its name - see more about getters and setters here).

Now let’s get our loop. One detail is that the method Scanner::next will only read the entry until you find a space, so if the name typed is "Fulano de Tal", the method next() only returns "John Doe" (and the next call next() would read the "of"). We can resolve this by exchanging the calls of next() for nextLine(), which consumes the entire input until it finds a line break (in this case, the ENTER typed by the user). So would be:

Scanner scanner = new Scanner(System.in);
List<Agenda> lista = new ArrayList<Agenda>();
String resp;
do {
    System.out.println("Digite o nome");
    lista.add(new Agenda(scanner.nextLine()));

    System.out.println("Deseja digitar outro ? ");
    resp = scanner.nextLine();
} while (resp.equalsIgnoreCase("Y")); // enquanto resp for Y, continua no loop

In other words, I read a name, create an agenda with that name and add it to the list. Then I ask if the user wants to enter another name, and based on the answer, it continues or not in the do/while. If you want, it can also be:

while (true) {
    System.out.println("Digite o nome");
    lista.add(new Agenda(scanner.nextLine()));

    System.out.println("Deseja digitar outro ? ");
    if (! "Y".equalsIgnoreCase(scanner.nextLine()))
        break;  // se usuário digitou algo diferente de Y, interrompe o while
}

In the case, the break interrupts the loop.

Finally, just print the list, making a for by its elements and printing one by one:

for (Agenda agenda : lista) {
    System.out.println(agenda.getNome());
}

Answer 2

You could do a for that traverses an array at the same time that asks the question, then if the question is "Y" it would save at position 0 of the array the string typed, after typing it would redo the question and then if the answer is "Y" it would save the entered value at position 1 of the array, if the answers are different from "Y" it would close the for question and then show the array. Remembering that when displaying an array one needs a go to traverse it. Good luck!