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Controlling the Selected Elements of an ArrayList

I have ArrayList

of Client

:

ArrayList<Client> clients = new ArrayList<>();

These clients are displayed in a list and the user can "select" one or more clients. This means that each client may or may not be selected, and there is no need to store this value outside of the screen where the list is displayed. I want this custom selection to work with it (like checking a checkbox in a list box), but I was wondering what is the best way to do it. What I have tried:

  • Add a boolean field selected

    to the class Client

    . I don't like this option as the selected is not the original property Client

    and it doesn't make sense on it.
  • Expands Client

    in SelectableClient

    and adds a boolean field selected

    .
  • You have a secondary array (or ArrayList or whatever) that controls the selected status.
  • Use a structure Map<boolean, Client>

    , but I am not sure about this option as I am adding and removing clients from the array.

Which of these options are most effective and easier to implement?

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3 answers


I would recommend using Set<Client>

(for example HashSet<Client>

) and adding selected clients to this set.

This avoids adding a field to Client

that doesn't really belong to that class.



Note that if you are using JList

for example you can use ListModel

/ directly ListSelectionModel

. (You don't need to create / maintain a data structure to host the selected clients yourself.)

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Add boolean field selected for Client class

As you already pointed out, the selected state is not a client property, but a user property. If you have multiple users, one user can select a customer and the other cannot. Therefore, the selection must be kept in the user's area.

Usage Set<Client>

, as already suggested, seems like a better data structure as it avoids duplication and thus clients can be safely canceled with remove()

.



Extends client to SelectableClient

This approach has the same problem, the selection state is modeled as a property of the client, not the user.

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I would recommend that you create a new generic class sth like this:

class SelectableItem<T> {
    private T item;
    private boolean selected;

    public SelectableItem(T item, boolean selected) {
         ....
    }
    // getters setters
}

and create an array or set of that type. This way you only have one additional class and you can reuse it later for other use cases.

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