java - 我需要创建一个访问器方法，该方法将返回最后一个被划掉的数字

Question

我的 Java 作业包括创建一个名为 Qwixx 的棋盘游戏。您掷骰子并划掉游戏板上的数字，其中有 2 行从 2-12 开始，另外 2 行从 12-2 开始。我的问题是创建访问器方法来获取每行最后划掉的数字。最后划掉的数字应该是距离游戏板右侧最远的数字。这就是我的 Player 类:

public class Player {
    private String[][] gameBoard = new String[4][11];
    private int lastCrossedOffR;

    //default constuctor 
    public Player() {
        lastCrossedOffR = 0;
        initializeGameboard();
    }

    //get method to obtain the last number that has been crossed off
    public int getLastCrossedOffR() {
        for(int j = 0; j<gameBoard[0].length;) {
            if (gameBoard[0][j] == "X") {
                if (j == 0)
                    lastCrossedOffR = 2;
                else if (j == 1)
                    lastCrossedOffR = 3;
                else if (j == 2)
                    lastCrossedOffR = 4;
                else if (j == 3)
                    lastCrossedOffR = 5;
                else if (j == 4)
                    lastCrossedOffR = 6;
                else if (j == 5)
                    lastCrossedOffR = 7;
                else if (j == 6)
                    lastCrossedOffR = 8;
                else if (j == 7)
                    lastCrossedOffR = 9;
                else if (j == 8)
                    lastCrossedOffR = 10;
                else if (j == 9)
                    lastCrossedOffR = 11;
                else if (j == 10)
                    lastCrossedOffR = 12;
            } else {
                j++;
            }
        }
        return lastCrossedOffR;
    }

    //method that initializes each row of the game board 
    public void initializeGameboard() {
        for (int i = 0; i<gameBoard.length; i++) {
            for (int j = 0; j<gameBoard[i].length; j++) {
                if (i==0 || i==1) {
                    if (j==0) {gameBoard[i][j] = "2";} 
                    else if (j==1) {gameBoard[i][j] = "3";} 
                    else if (j==2) {gameBoard[i][j] = "X";} //i placed random x's to 
                    else if (j==3) {gameBoard[i][j] = "5";} //test out the get 
                    else if (j==4) {gameBoard[i][j] = "6";} //method
                    else if (j==5) {gameBoard[i][j] = "7";} 
                    else if (j==6) {gameBoard[i][j] = "X";} 
                    else if (j==7) {gameBoard[i][j] = "X";} //in my case, what the
                    else if (j==8) {gameBoard[i][j] = "10";} //get method should 
                    else if (j==9) {gameBoard[i][j] = "11";} //return is: 9
                    else if (j==10) {gameBoard[i][j] = "12";}

                } else if (i==2 || i==3) {
                    if (j==0) {gameBoard[i][j] = "12";} 
                    else if (j==1) {gameBoard[i][j] = "11";} 
                    else if (j==2) {gameBoard[i][j] = "10";} 
                    else if (j==3) {gameBoard[i][j] = "9";} 
                    else if (j==4) {gameBoard[i][j] = "8";} 
                    else if (j==5) {gameBoard[i][j] = "7";} 
                    else if (j==6) {gameBoard[i][j] = "6";} 
                    else if (j==7) {gameBoard[i][j] = "5";} 
                    else if (j==8) {gameBoard[i][j] = "4";} 
                    else if (j==9) {gameBoard[i][j] = "3";} 
                    else if (j==10) {gameBoard[i][j] = "2";}
                }
            }
        }
    }

这是我的驱动程序类:

public class Driver {

    public static void main(String[] args) {
        Player obj1 = new Player();
        obj1.printGameboard(); //assume this method is already created in the Player class
        System.out.print("The last crossed off number for the Red row is: " + obj1.getLastCrossedOffR());
    }
}

这是我运行代码时需要显示的内容:

player's gameboard: 
           Red: 1 2 3 X 5 6 7 X X 10 11 12
        Yellow: 1 2 3 4 5 6 7 8 9 10 11 12
         Green: 12 11 10 9 8 7 6 5 4 3 2 1
          Blue: 12 11 10 9 8 7 6 5 4 3 2 1

The last crossed off number for the Red row is: 9

请帮我弄清楚如何修复我的 getLastCrossedOffR() 方法!预先感谢您!

Answer 1

您的问题是您尝试将 String 与 == 进行比较，而不是使用 equals，请改用:

public int getLastCrossedOffR() {
    for(int j = 0; j < gameBoard[0].length;) {
        // was previously `gameBoard[0][j] == "X"`
        if ("X".equals(gameBoard[0][j])) {
            // ...

== 运算符比较变量中的字面意思。对于像 int 这样的原语来说这很好，因为它确实存储了原语值。但对于Object(例如String)，它存储对象引用。

假设 "X" 是一个 String，其引用为 Object #1 和 gameBoard[0][0] 存储 String 引用 Object #2。

调用 "X"== gameBoard[0][0] 就像调用 Object #1 == Object #2 一样，这是错误的。 (除非您已将Object #1存储在gameBoard[0][0]中)

但是调用 "X".equals(gameBoard[0][0]) 就像调用 Object #1.equals(Object #2) 一样，它会进入Object #1 的 equals 函数(又名 String.equals(Object o))并比较以下值的值这两个 String 而不是比较它们的引用。

经验法则是 == 仅适用于基元(int、float、long、 double 、短、字节、字符、 boolean )，但是对于其他所有内容，请使用 .equals (可能必须被覆盖)。