Creating an ArrayList of Subclass Objects

Question

I have a superclass Appointment that is then extended to a few different types of appointments. I need to make an ArrayList of appointments of different types which I did not think would be much of a problem since they all share a common superclass - Appointment. But when I try to add one of the subclasses Daily to the ArrayList<Appointment> book = new ArrayList<Appointment>() it fails to do so.

I have:

ArrayList<Appointment> book = new ArrayList<Appointment>()

Then later on in the program (I'm passing description, day, month, and year from the method it's place in):

book.add(new Daily(description, day, month, year));

And I get the suggestion of: The method add(AppointmentBook.Appointment) in the type ArrayList is not applicable for the arguments (Daily)

berko · Accepted Answer · 2017-03-10 17:07:48Z

1

Change your code from ArrayList<Appointment> to ArrayList<? extends Appointment>

answered Mar 10, 2017 at 17:07

berko

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2 Comments

user6096265 Over a year ago

Like ArrayList<? extends Appointment> book = new ArrayList<? extends Appointment>() ?

berko Over a year ago

Yes, although you only need to declare the type once. ArrayList<? extends Appointment> book = new ArrayList<>()

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