java - 摆脱二维 Java 数组中的自动填充零

Question

用户输入的数字每行最多 20 个，共 50 行。问题是，如果用户在一行中输入的整数少于 20 个，则数组的空白处将填充零，因此总共有 20 个。这会影响我使用数组完成的计算。

有谁知道一种有效的方法来消除这些零，以便只保留原始输入的数字？

//Extracting/reading from file
public void readFile(File file) {

    try {
        //creates scanner to read file
        Scanner scn = new Scanner(file);

        //set initial count (of rows) to zero
        int maxrows = 0;

        //sets columns to 20 (every row has 20 integers - filled w zeros if not 20 inputted)
        int maxcolumns = 20;

        // goes through file and counts number of rows to set array parameter for length
        while (scn.hasNextLine()) {
            maxrows++;
            scn.nextLine();
        }

        // create array of counted size
        int[][] array = new int[maxrows][maxcolumns];

        //new scanner to reset (read file from beginning again)
        Scanner scn2 = new Scanner(file);

        //places integers one by one into array
        for (int row = 0; row < maxrows; row++) {
            Scanner lineScan = new Scanner(scn2.nextLine());
            //checks if row has integers
            if (lineScan.hasNextInt()) {

                for (int column = 0; lineScan.hasNextInt(); column++) {
                    array[row][column] = Integer.parseInt(lineScan.next());
                }

            } else System.out.println("ERROR: Row " + (row + 1) + " has no integers.");
        }
        rawData = array;
    }
}

Answer 1

您应该查看List。既然您承认您不知道要插入多少元素，那么我们可以简单地用用户想要添加的元素来扩展列表。

// Initialize the initial capacity of your dataMatrix to "maxRows",
// which is NOT a hard restriction on the size of the list
List<List<Integer>> dataMatrix = new ArrayList<>(maxrows);

// When you want to add new elements to that, you must create a new `List` first...

for (int row = 0 ; row < maxrows ; row++) {
    if (lineScan.hasNextInt()) {
        List<Integer> matrixRow = new ArrayList<>();
        for (int column = 0; lineScan.hasNextInt(); column++) {
            dataMatrix.add(Integer.parseInt(lineScan.next()));
        }
        // ...then add the list to your dataMatrix.
        dataMatrix.add(matrixRow);
    }
}