从文件中获取整数值到数组

Question

我试图通过分隔逗号从文件中获取整数值并将它们放入二维数组中。 文件是这样的；

0,7,9,0,0,14
7,0,10,15,0,0
9,10,0,11,0,2
0,15,11,0,6,0
0,0,0,6,0,9
14,0,2,0,9,0

所以我希望第一行在数组 [0][0 到 5] 中，其他行也相同，例如数组 [2][1] 必须为 10。但我无法弄清楚算法这里根本没有二维数组。

public static void main(String[] args) throws FileNotFoundException {
    BufferedReader reader = new BufferedReader(new FileReader("file.txt"));
    Scanner sc = new Scanner(reader);
    int[][] array = new int[6][6];

    while(sc.hasNextLine()){
        String line = sc.nextLine();
        String[] str = line.split(",");

        for (int i = 0; i < 6; i++) {
                for (int j = 0; j < 6; j++) {
                    array[i][j] = Integer.valueOf(str[i]);
                }
        }
    }
}

Answer 1

您正在遍历每一行的每个值。您的索引之一需要是线，另一个需要是线内的位置。您只需要一个for 循环；您应该在 while 循环中增加另一个索引。

public static void main(String[] args) throws FileNotFoundException {
    BufferedReader reader = new BufferedReader(new FileReader("file.txt"));
    Scanner sc = new Scanner(reader);
    int[][] array = new int[6][6];
    int i=0;
    while(sc.hasNextLine()){
        String line = sc.nextLine();
        String[] str = line.split(",");
        for (int j = 0; j < 6; j++) {
            array[i][j] = Integer.valueOf(str[j]);
        }
        i++;
    }
}

您还应该考虑，如果文件超过 6 行或超过 6 行，这将失败，因此这不是非常健壮的代码。完成读取文件后，最好填充不同的（动态）数据类型并转换为数组。至少，您应该检查自己没有超出预期的指数范围。

Answer 2

你可以这样做。关键是Java中没有真正的多维数组。只是可以容纳数组的单个 D 数组。

        // allocate the "2D" array but no need to specify the rows.
        int[][] array = new int[6][];

        // starting row number
        int rowNumber = 0;

        while(sc.hasNextLine()){
            String line = sc.nextLine();
            System.out.println(line);
            String[] str = line.split(",");

            // here is where your code differs
            // allocate a new row based on length of items just read
            int[] row = new int[str.length];

            // Now copy and convert to ints.
            for (int i = 0; i < str.length; i++) {
                row[i] = Integer.parseInt(str[i]);
            }
            // Then just assign the row to the row number.
            // you can do this because a two dimentional array is just an
            // one dimenional array of another one dimensional array.
            array[rowNumber++] = row;
        }
        // print them out for verification.
        // get each row (from the array of rows)
        for (int[] row : array) {
            System.out.println(Arrays.toString(row));
        }

那么做了什么就像下面这样;

int [][] matrix = new int[2][];
matrix[0] = new int[]{1,2,3,4};
// rows can be different sizes.
matrix[1] = new int[]{1,2,3,4,5,6,7};      

for (int i = 0; i <2; i++) {
   int[] row  = matrix[i];
   for (int j = 0; j < row.length; j++) {
        System.out.print(row[j] + " " );
   }
   System.out.println(); // next line
} 

Answer 3

这是一种更现代的方法，使用 NIO 和 Streams：

int[][] read2dArrayFromFile(String path) throws IOException {
    return Files.readAllLines(Paths.get(path))
                .stream()
                .map(line ->
                         Arrays.stream(
                             line.split("\\D+")  // split by anything that's not a digit
                         ).mapToInt(Integer::parseInt).toArray()
                ).toArray(int[][]::new);
}