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I cannot get the properties of a certain card in this code it always prints null and I don't know why. I'm from Php-HTML world and I'm a newbie on JAVA.

This is the from Opportunity.java

package opportunity; import java.io.*; import java.util.Collections; import java.util.List; import static java.util.stream.Collectors.toList; import java.util.stream.IntStream; import java.util.stream.Stream; import opportunity.Card.CardType; public class Opportunity { /*Player 1 */ public int p1_money = 10000; public int p1_card_d = 40; public int p1_card_h = 0; /*Player 2 */ public int p2_money = 10000; public int p2_card_d = 40; public int p2_card_h = 0; /** * @param args the command line arguments * @throws java.io.IOException */ public static void main(String[] args) throws IOException { System.out.print("***************Opportunity***************\n"); final Card card1 = new Card(Card.CardType.EVENT, "Get Tax Returns"). setProperty("cost", "0.00"). setProperty("Effect", "Effect: Earn money equal to the\n" + "maximum income each of your\n" + "properties can give you,\n" + "depending on their level."); final Card card2 = new Card(Card.CardType.EVENT, "BIR Hunting Begins"). setProperty("cost", "0.00"). setProperty("Effect", "Effect: An opponent loses\n" + "money equal to 50% of the\n" + "maximum income each of\n" + "their properties can give him or her,\n" + "depending on the level of the\n" + "property."); final Card card3 = new Card(Card.CardType.EVENT, "Restore Balance"). setProperty("cost", "10000.00"). setProperty("Effect", "Effect: The total income of all\n" + "the players becomes equal to\n" + "the income of the player\n" + "with the lowest income."); final List<Card> deck = Stream.of(CardType.values()). flatMap(type -> IntStream.rangeClosed(1, 4).mapToObj(num -> new Card(type, "CardName" + num))). collect(toList()); Collections.shuffle(deck); System.out.println(deck.get(0).getProperty("Effect")); } }

And This is the codes from Card.java

package opportunity; import java.util.*; public class Card { public enum CardType { EVENT, PROPERTY, ASSET; } private final CardType cardType; private final String cardName; private final Map<String, String> properties = new HashMap<>(); Card(final CardType cardType, final String cardName) { this.cardType = cardType; this.cardName = cardName; } public Card setProperty(final String name, final String value) { properties.put(name, value); return this; } public String getProperty(final String name) { return properties.get(name); } }

It always returns this: 

run: ***************Opportunity*************** null BUILD SUCCESSFUL (total time: 0 seconds)

even though I put an index on get()

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2
  • Please describe your code in brief and tell what you tried to solve the problem. Commented Aug 24, 2014 at 18:05
  • It doesn't look like you're adding the cards to the deck. I'm not sure what your lambda function is trying to do, but it'd be easier to just add to an ArrayList. Commented Aug 24, 2014 at 18:06

3 Answers 3

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To build on @Luiggi Mendoza's answer, you are not adding your Card objects to the deck list.

Replace

final List<Card> deck = Stream.of(CardType.values()). flatMap(type -> IntStream.rangeClosed(1, 4).mapToObj(num -> new Card(type, "CardName" + num))). collect(toList());

With 

final List<Card> deck = new ArrayList<>(); deck.add(card1); deck.add(card2); deck.add(card3);

Instead of adding new Cards to the list, add the objects you have already created - and have properties set.

Edit: to address your comment

final List<Card> deck = new ArrayList<>(); for (int i=0; i<4; i++) { deck.add(card1); deck.add(card2); deck.add(card3); }

This will add four copies of each of your three cards to the list.

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1 Comment

But the one that you want me to replace create 4 copies of the card. so there must be a total of 12 cards, 4 of the card1, 4 of the card2, 4 of the card3.
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Here:

final List<Card> deck = Stream.of(CardType.values()). flatMap(type -> IntStream.rangeClosed(1, 4).mapToObj(num -> new Card(type, "CardName" + num))). collect(toList()); Collections.shuffle(deck);

You fill List<Card> deck with new Cards, you don't add any of the other cardX variables. Thus, when retrieving this "Effect" property, you get null because the Cards in deck don't have the "Effect" property set before.

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0

The comment of the previous folk is totally right. You are not adding the created cards to the list.

Try replacing your code

final List<Card> deck = Stream.of(CardType.values()). flatMap(type -> IntStream.rangeClosed(1, 4).mapToObj(num -> new Card(type, "CardName" + num))). collect(toList());

for standard list creation and adding. For instance (and updated for 4 cards):

List<Card> deck = new ArrayList<Card>(); for (int i = 0; i < 4; i++){ deck.add(card1); deck.add(card2); deck.add(card3); }

If you want to minimise the number of lines of code, there are ways to initialise a new list with content. Try this post Initialization of an ArrayList in one line.

Anyway, always try to code the simplest solution, even more when starting with a new language.

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1 Comment

The code that you want me to replace creates 12 cards to make a deck. 4 card1, 4 card2, 4 card3.

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