Compiler thinks I am calling a variable from another class in a static context, but I'm not

Question

I would like my dealer class in a BlackJack project to print the top two "cards" of an arrayList "theDeck". I am getting a compiler error (shown later) and can't figure out what it means. This is my code for a class "Deck" that makes a deck of cards, shuffles them, and puts them in an arrayList "theDeck":

 *  Compilation:  javac Deck.java
 *  Execution:    java Deck
 *  Author:       Aidan Hill
 *  Status:       Working
 *  Priority:     None
 *
 ******************************************************************************/
import java.util.ArrayList;
/******************************************************************************/


public class Deck extends Game {
   int n;
   //Deck deck = new Deck();
   String[] deckArray = new String[n];
   String[] SUITS = {
         "Diamonds", "Clubs", "Spades", "Hearts"
         };

   String[] RANKS = {
         "2", "3", "4", "5", "6", "7", "8", "9", "10",
         "Jack", "Queen", "King", "Ace"
         };

   public Deck() {
      // constructor
      n = SUITS.length * RANKS.length;
      deckArray = new String[n];
      for (int i = 0; i < RANKS.length; i++) {
         for (int j = 0; j < SUITS.length; j++) {
            deckArray[SUITS.length*i + j] = RANKS[i] + " of " + SUITS[j];
         }
      }
   }


   public String shuffleDeck() {
      // shuffle the deck
      int i;
      for (i = 0; i < n; i++) {
         int r = i + (int) ((n - i) * Math.random());
         String temporary = deckArray[r];
         deckArray[r] = deckArray[i];
         deckArray[i] = temporary;
      }
      return deckArray[i - 1];
   }


   public ArrayList<String> theDeck() {
   // save shuffled deck in an arraylist
      ArrayList<String> theDeck = new ArrayList<String>();
      for (int i = 0; i < n; i++) {
         theDeck.add(deckArray[i]);
      }
      return theDeck;
   }
}

This is my code for another class "Dealer" that will take the top two elements of arrayList "theDeck" and print them to the console:

 /******************************************************************************
 *  Compilation:  javac Dealer.java
 *  Execution:    java Dealer
 *  Author:       Aidan Hill
 *  Status:       Under Construction
 *  Priority:     !
 *
 ******************************************************************************/
import java.util.ArrayList;
import java.util.ArrayList;

/******************************************************************************/


public class Dealer extends Game {


   public ArrayList<String> dealSumCards() {
      ArrayList<String> hand = new ArrayList<String>();
      hand.add(Deck.theDeck().toString());
      System.out.println("The first hand is: " + hand);
      return hand;
   }
}

When I attempt to compile, I get this error message:

 ----jGRASP exec: javac -encoding UTF-8 -g @BlackJack_source_files_1638219710914506414jgr
Dealer.java:20: error: non-static method theDeck() cannot be referenced from a static context
      hand.add(Deck.theDeck().toString());
                   ^
1 error

 ----jGRASP wedge2: exit code for process is 1.
 ----jGRASP: operation complete.

Whats my error? Neither method is static... Am I big stupid? I tried changing dealer to extend game instead of deck and vise versa, same problem. (If you need any more code, let me know, and I will edit the post.)
Edit: I realize now that there are many many related questions. Sorry lol. Please be patient with me, new to coding and this website.

Answer 1

Deck is the name of a class. theDeck() is not a class method; you have to call it on an instance of the class.

There are two ways you could get this to work. One way would be to instantiate a Deck object, and call theDeck() on it:

Deck deck = new Deck();
hand.add(deck.theDeck().toString());

Another would be to make theDeck() static:

public static ArrayList<String> theDeck() {
// save shuffled deck in an arraylist
   ArrayList<String> theDeck = new ArrayList<String>();
   for (int i = 0; i < n; i++) {
      theDeck.add(deckArray[i]);
   }
   return theDeck;
}

This would make Deck.theDeck() work - except that n is a non-static field; you'd need to make it static or pass it in as a method parameter.