Question

I have CardType1 and CardType2 that extends Card, and an Area that has an ArrayList of Card. This array will be filled with CardType1 and CardType2 objects, but I need to eventually access them like:

for (CardType1 card : this.cards) { ...

An overview:

public class Area {

    List<Card> cards = new ArrayList<Card>();
    ..
}

public class Card {..}

public class CardType1 extends Card {..}

public class CardType2 extends Card {..}

How can I iterate over only one of the subtypes in my List<Card> cards list?

Answer 1

You cannot do it this way, because the type of object in cards, is Card, not CardType1:

for(CardType1 card : this.cards){ ...

You can however do this:

for(Card card : this.cards) {
    if (card instanceof CardType1) {
        CardType1 card1 = (CardType1) card;
        // do something with the card1
    } else {
        CardType2 card2 = (CardType2) card;
        // do something with the card2
    }
 }

What I am doing here, is iterating through the cards, as you were (except my type is the most general type to both besides Object). Then I check if the card is of type CardType1, or CardType2, using the instanceOf operator and cast it to that type, then handle it.