I have to make a "guess next card is higher" game. but can't find the problem

3 classes. Card, Game & Deck. I don't know why it is giving me an error. Wish someone can help me out, I would like to know what the problem is.

What the title say's, I have to guess if the next card that I would get is higher or lower.

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package CardGame;

import java.util.Scanner; import java.util.*;

public class Game {

private static int score;

// currentCard : Card
private static Card currentCard;
// Next Card
private Card nextCard;
// Scanner
private static Deck deck;

private static Scanner sc = new Scanner(System.in);

// Main

public static void main(String[] args) {

    deck = new Deck();

    currentCard = deck.getNextCard();

    Game.gameTurn();
}

// get turn method
public static void gameTurn() {
    // System.out.println(Deck.getCards().size());
    System.out.print("is your next card higher or lower than the next card?");
    System.out.print(sc);
    String answer = sc.nextLine();

    Card nextCard = deck.getNextCard();


    if (answer.equals("higher") && nextCard.isHigherOrEqual(currentCard)) {

        correct();
    } else if (answer.equals("lower") && !nextCard.isHigherOrEqual(currentCard)) {
        correct();
        // answer.equals("lower")&& !nextCard.isHigherOrEqual(currentCard)
    } else {
        gameOver();
    }
}

// correct method

public static void correct() {
    Game.gameTurn();
    score = 0;
    score++;
}

// Game over Method

public static void gameOver() {
    System.out.println("total score is " + score + "!");
}

}

package CardGame;

import java.util.ArrayList; import java.util.Collections;

public class Deck {

// cards = Card = new ArrayList<>()
private static ArrayList<Card> cards = new ArrayList<>();

// Deck Method
public void Deck() {

    for (int i = 1; i < 4; i++) {
        String suits;

        switch (i) {

        case 1:
            suits = "Hearts";
            break;

        case 2:
            suits = "Diamonds";
            break;

        case 3:
            suits = "Spades";
            break;

        case 4:
            suits = "Clubs";
            break;
        default:
            suits = "";
            break;
        }
        for (int j = 1; j <= 10; j++) {
            int value = j;
            String name = j + " of " + suits;
            Card c = new Card(suits, name, value);

            cards.add(c);

        }
        // add 1.3 tot 1.11

        Card jack = new Card(suits, "jack of " + suits, 11);

        cards.add(jack); // JACK

        Card queen = new Card(suits, "queen of " + suits, 12);

        cards.add(queen); // QUEEN

        Card king = new Card(suits, "king of " + suits, 13);

        cards.add(king); // KING

        Card ace = new Card(suits, "ace of " + suits, 14);

    }
    // 1.11 shuffle cards
    Collections.shuffle(cards);
}

// getNextCard() : Card

public Card getNextCard() {

    Card nextCard = cards.remove(0);

    return nextCard;

}

// getCards() : ArrayList <card>
public static ArrayList<Card> getCards() {

    return cards;
}

}

package CardGame;

public class Card {

// Suit String
private String suit;

// Name String
private String name;
// Value int
private int value;

// Card constructor
public Card(String suit, String name, int value) {
    this.value = value;
    this.name = name;
    this.suit = suit;

}

public int getValue() {
    return value;
}

// toString Method
public String toString() {
    if (value == 15);
    return "";
}
// isHigherorEqual Method

public boolean isHigherOrEqual(Card c) {
    if (this.value >= c.getValue()) {
        return true;
    } else {
        return false;
    }
}

}