Difference in output - Java

Question

There isn't an error message appearing in my code. However, I get different outputs when I type my code in the main and when i call my methods.

package card;

import java.util.Arrays;
import java.util.Random;

/**
 *

 */
public class Card {

    /**
     * @param args the command line arguments
     */
    static String rank;
    static String suit;
    static String[] ranks = {"2","3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"};
    static String[] suits = {"Spades","Hearts", "Clubs", "Diamonds"};
    static Card[] deck = new Card[52];

   public Card(String rank, String suit)
   {
      this.rank = rank;
      this.suit = suit;
   }

   public static String getRank()
   {
       return rank;
   }

   public static void setRank(String r)
   {
       rank = r;
   }

    public static String getSuit()
   {
       return suit;
   }

   public static void setSuit(String s)
   {
       suit = s;
   }





    public static void init(Card[] deck)
    {
        for(int x = 0; x<deck.length; x++)
        {
            Card newCard = new Card(ranks[x%13], suits[x/13]);
            deck[x] = newCard;
        }
    }

    public static void swap(Card[] deck, int a, int b)
    {
        Card temp = deck[a];
        deck[a] = deck[b];
        deck[b] = temp;
    }

    public static void shuffle(Card[] deck)
    {
        Random rnd = new Random();
        for(int x = 0; x<deck.length; x++)
        {
            swap(deck, x, (rnd.nextInt(deck.length)));
        }
    }

    public static void print(Card[] deck)
    {   
        for(int x =0; x<deck.length; x++)
        {
              System.out.println(deck[x].getRank() + " of " + deck[x].getSuit());
        }

    }


    public static void main(String[] args) {
        // TODO code application logic here


    for(int x = 0; x<deck.length; x++)
    {
        Card cards = new Card(ranks[x%13], suits[x/13]);
        deck[x] = cards;
        System.out.println(deck[x].getRank() + " of " + deck[x].getSuit());

        //init(deck);
        //print(deck);
    }


  }

}

For doing my codes in the main manually without any methods, i will get the correct output:

Eg

10 of Diamonds
J of Diamonds
Q of Diamonds
K of Diamonds

But when i call the methods, i get the following output:

A of Diamonds
A of Diamonds
A of Diamonds
A of Diamonds
A of Diamonds

Whats wrong?

What do you mean "when i invoke the methods"? How are you running them without running the main method? — Andy Turner
– Andy Turner, Commented Jun 30, 2016 at 11:25
Have you tried to use a Debugger to find out what is happend? — Jens
– Jens, Commented Jun 30, 2016 at 11:26

Eran · Accepted Answer · 2016-06-30 11:26:11Z

2

Your following static members

static String rank;
static String suit;

shouldn't be static, since each Card should have different values :

String rank;
String suit;

answered Jun 30, 2016 at 11:26

Eran

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4 Comments

Aloysius Over a year ago

thank you. from my understanding, doesn't static refers to attribute that belongs to the class?

Eran Over a year ago

@Aloysius static means that all instances of the class share a single instance of the static variable. Hence all Card instances have the same rank and suit in your case.

Aloysius Over a year ago

Oh, as in the variable value won't change. am i right to say this?

Eran Over a year ago

@Aloysius It will change whenever you assign a new value to it, but each time you change it, that change will be seen by all the Card instances.

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