java - 私有(private)最终 int 空白；私有(private)最终int空白j；

Question

我有这个代码:

public final class Board {

    private final int[][] blocks;
    private final int N;
    private final int blanki;
    private final int blankj;
    int i, j;

    // construct a board from an N-by-N array of blocks
   public Board(int[][] blocks)  {

        this.blocks = new int[blocks.length][blocks.length];

        for(i = 0; i < blocks.length; i++){
            for(j = 0; j < blocks.length; j++){
                this.blocks[i][j] = blocks[i][j];
                if(blocks[i][j] == 0) {
                    int f = i;
                    int c = j;
                }
            }
        }
        this.N = this.dimension();
        this.blanki = f;
        this.blankj = c;
    }

}

并出现以下错误:

文件:C:\Users\cbozanic\algs4\Board.java [行:28] 错误:f 无法解析为变量 文件:C:\Users\cbozanic\algs4\Board.java [行:29] 错误:c 无法解析为变量 文件:C:\Users\cbozanic\algs4\Board.java [行:159] 错误:局部变量 s 可能尚未初始化

我真的不明白我做错了什么!任何帮助将不胜感激。

Answer 1

f 和 c 是在 for 循环的范围内定义的。它们在外部是不可见的:

this.blocks = new int[blocks.length][blocks.length];

for(i = 0; i < blocks.length; i++){
    for(j = 0; j < blocks.length; j++){
            int f = i;
            int c = j;
    } //From this point, f and c are not defined anymore
}
}
this.N = this.dimension();
this.blanki = f; //Here, f does not exist
this.blankj = c; //Here, c does not exist

如果您想使用 f 和 c，请在循环之前声明它们:

int f = ...
int c = ...

 for(i = 0; i < blocks.length; i++){
    for(j = 0; j < blocks.length; j++){
            f = ...;
            c = ...;
    }
}

对于消息局部变量 s 可能尚未初始化，这意味着您声明并使用了该变量而没有对其进行初始化。例如:

int s; //For example, int s = 0; would make sense.
s++;

注意:创建新实例时，类属性采用默认值，但局部变量保持“未初始化”状态。