在公共类中使用包私有类

Question

我想创建一个称为对的简单纸牌游戏。 基本上，一个玩家一次掷出2张牌，如果有2张牌匹配，它们将保持正面朝上。 如果不匹配，则将它们反转回到正面朝下的位置。 我创建了一个包私有类Card包，用于存储该卡的实际值（字符）以及是否翻转（面朝上）。 但是我得到了错误

MatchCardGame.java:57: error: cannot find symbol
            showBoard[i-1] = tempCard2.value + "(" + i + ") ";
                                      ^
  symbol:   variable value
  location: variable tempCard2 of type Card
MatchCardGame.java:61: error: cannot find symbol
            showBoard[i-1] = tempCard1.value + "(" + i + ")";
                                      ^
  symbol:   variable value
  location: variable tempCard1 of type Card
2 errors

当我尝试运行以下代码时...

public class MatchCardGame {

    public char[] gameCards;
    int gcCount, showCount;
    String[] showBoard;
    char firstCard = 'a';
    char cardValue;
    Card tempCard1, tempCard2;
    int flipCount = 0;

    public MatchCardGame(int n){ // n is the size of the game set by the player in the main, it could only be a multiply of four

        // Check if input n is valid
        if ((n % 4) != 0 || n < 4 || n > 104) System.exit(0);

        // Create an array of cards used in the game
        // here we're using a-z as cards thus min = 4 and max = 26*4
        gcCount = 0;
        gameCards = new char[n];
        for (int i = 0;i < (n / 4); i++){
            for (int j = 0; j < 4; j++){
                gameCards[gcCount] = firstCard;
                gcCount++;
            }
            firstCard++;
        }

        // Display the back of the cards array
        showCount = 1;
        showBoard = new String[n];
        for (int i = 0; i < n; i++){
            showBoard[showCount-1] = "X(" + showCount + ") ";
            showCount++;
        }

        // Create an array of object card, assign each card with a corresponding value in the gameCards array
        Card[] cardArray = new Card[n];
        for (int i = 0; i < cardArray.length; i++){
            cardArray[i] = new Card(gameCards[i]);
        }

    }

    // String representation of cards array
    public String boardToString(){
        StringBuilder builder = new StringBuilder();
        for(String board : showBoard){
            builder.append(board);
        }
        return builder.toString();
    }

    // flip the card - if already faced up or picked an invalid card, don't flip
    public boolean flip (int i){
        if (flipCount % 2 == 0){
            tempCard2 = new Card(gameCards[i-1]);
            showBoard[i-1] = tempCard2.value + "(" + i + ") ";
            tempCard2.flipped = true;
        }else{
            tempCard1 = new Card(gameCards[i-1]);
            showBoard[i-1] = tempCard1.value + "(" + i + ")";
            tempCard1.flipped = true;
        }
        flipCount++;
        return true;
    }

    // returns true if card1 and card2 are matched - only executes when an even # of flips are made
    // public boolean wasMatch(){}

    // if card1 and card2 create a mismatch, reverse them back to faced down position
    // public void flipMismatch(){}

    // if all cards are flipped and matched, game is over
    // public boolean gameOver(){}

    // count the # of flips made during the game
    // public int getFlips(){}

    public static void main(String[] args) {
        //set up reader to take inputs
        java.util.Scanner reader = new java.util.Scanner (System.in);

        int n = 16; //game size

        MatchCardGame g1 = new MatchCardGame(n);
        System.out.println(g1.boardToString());
        g1.flip(5);
        System.out.println(g1.boardToString());
    }


}

class Card{
    boolean flipped; // check if card is flipped
    Card(char value){
        value = value;
    }
}

正确的语法是什么？ 还是有任何更简单的方式编写此游戏？ （保持方法...）

Answer 1

您的卡类不正确：

class Card{
    boolean flipped; //This is an attribute
    Card(char value){
        value = value; // This line does nothing!!!
    }
}

我想你的课应该是这样的：

class Card{
    boolean flipped; // check if card is flipped
    char value;
    Card(char val){
        this.value = val; // "this" is not necessary, but makes it more readable
    }

}

Answer 2

您正在从Card类访问值，但从未声明该变量。像这样更改Card类，它将起作用

class Card{
    boolean flipped; // check if card is flipped
    char value;
    Card(char value){
        value = value;
    }
}

Answer 3

您的错误来自您错过了Card类中的value字段的事实。

class Card{
    boolean flipped; // check if card is flipped
    char value;
    Card(char value){
        this.value = value;
    }
}

Answer 4

卡类没有任何值名称的数据成员。

这是您的卡类代码

class Card{
    boolean flipped; // check if card is flipped
    Card(char value){
        value = value;
    }
}

因此，您需要在Card Class中创建值作为数据成员

样例代码

    class Card{
        boolean flipped; // check if card is flipped
        char value;   //here you need to create value data member 
       //datatype you can change according to your requirement 

       Card(char value){
                this.value = value; //here need to write this.value because you want assign value to class member
            }
        }

希望对您有帮助。