试图创建一个返回二维数组的函数，在函数内部使用开关。获取“重复的局部变量”警告

Question

public class Apples {
    
    static char[][]createBoard(int boardType){ 
        char[][] board = new char [8][10];
        switch (boardType){
            case 1:
                char board[][] = {{' ','1','2','3','4','5','6','7','8','9'},{'1','#','#','#','-','@','-','#','#','#'},{'2','#','#','-','@','@','@','-','#','#'},{'3','#','-','@','@','-','@','@','-','#'},{'4','-','@','@','@','@','@','@','-'}};
                break;
            case 2: 
                char board[][] = {{' ','1','2','3','4','5'},{'1','-','-','-','-','-'},{'2','-','@','@','@','-'},{'3','-','-','@','-','-'},{'4','-','-','@','-','-'},{'5','-','-','-','-','-'}};
                break;
        }
        return board;
    }   
    
    public static void main (String args[]) {
        System.out.println("This is your array :");
        
        char chosenboard[][] = createBoard(2);
        for (int row = 0; row < chosenboard.length; row++) {
            for (int column = 0; column < chosenboard[row].length; column++) {
                System.out.print(chosenboard[row][column]); 
            }
        }
    }
}

public class Apples {
    

    static char[][]createBoard(int boardType){ 
        char[][]board;
        switch (boardType){
            case 1:
                board = new char[][] {{' ','1','2','3','4','5','6','7','8','9'},{'1','#','#','#','-','@','-','#','#','#'},{'2','#','#','-','@','@','@','-','#','#'},{'3','#','-','@','@','-','@','@','-','#'},{'4','-','@','@','@','@','@','@','-'}};
                break;                          
            case 2: 
                board = new char[][] {{' ','1','2','3','4','5'},{'1','-','-','-','-','-'},{'2','-','@','@','@','-'},{'3','-','-','@','-','-'},{'4','-','-','@','-','-'},{'5','-','-','-','-','-'}}; //here I am declaring and assigning again
                break;
            
        }
        return board;
                }
                                
    
    public static void main (String args[]) {       
        System.out.println("This is your array :"); 
            char chosenboard[][] = createBoard(2);
            for (int row = 0; row <chosenboard.length; row++) {
                for (int column = 0; column < chosenboard[row].length; column++) {
                    System.out.print(chosenboard[row][column]); 
            }
    
    }

}
}

以前的错误“重复的局部变量”消失了，但我得到了一个新的错误在我的返回板行。它说“本地可变板可能尚未初始化”

Answer 1

您的代码没有编译，因为变量board已经在switch语句之前定义，并且不能（在该范围内）再次定义。

static char[][] createBoard(int boardType) {
  char[][] board = new char[8][10];          // <= declared and assigned
  switch (boardType) {
    case 1:
      char board[][] = {{' ', /* ... */ }};  // <= declared and assigned again

在case中，您可以创建一个新的2D数组，然后将其赋给已经声明的变量，如下所示：

char[][] board; // declaration
board = new char[][]{{' ', '1', '2', '3', '4', '5', '6', '7', '8', '9'}, {'1', '#', '#', '#', '-', '@', '-', '#', '#', '#'}, {'2', '#', '#', '-', '@', '@', '@', '-', '#', '#'}, {'3', '#', '-', '@', '@', '-', '@', '@', '-', '#'}, {'4', '-', '@', '@', '@', '@', '@', '@', '-'}};

仔细看一下您的方法createboard所做的事情，您可以进一步简化它，直接构造并返回二维数组：

static char[][] createBoard(int boardType) {
    switch (boardType) {
        case 1:
            return new char[][]{{' ', '1', '2', '3', '4', '5', '6', '7', '8', '9'}, {'1', '#', '#', '#', '-', '@', '-', '#', '#', '#'}, {'2', '#', '#', '-', '@', '@', '@', '-', '#', '#'}, {'3', '#', '-', '@', '@', '-', '@', '@', '-', '#'}, {'4', '-', '@', '@', '@', '@', '@', '@', '-'}};
        case 2:
            return new char[][]{{' ', '1', '2', '3', '4', '5'}, {'1', '-', '-', '-', '-', '-'}, {'2', '-', '@', '@', '@', '-'}, {'3', '-', '-', '@', '-', '-'}, {'4', '-', '-', '@', '-', '-'}, {'5', '-', '-', '-', '-', '-'}};
        default:
            return new char [8][10];
    }
}