java读取文本数据，将数据保存为二维数组。

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利用BufferedReader和FileInputStream都可以实现读取文本数据，不同的是BufferedReader适用于读取文本较小的场景，因其会将文件所有行都存入内存中。

1.BufferedReader实现读取文本数据，并保存为二维数组。

private static double[][] getFile(String pathName) throws Exception {
        File file = new File(pathName);
        if (!file.exists())
            throw new RuntimeException("Not File!");
        BufferedReader br = new BufferedReader(new FileReader(file));
        String str;
        List<double[]> list = new ArrayList<double[]>();
        while ((str = br.readLine()) != null) {
            int s = 0;
            String[] arr = str.split(",");
            double[] dArr = new double[arr.length];
            for (String ss : arr) {
                if (ss != null) {
                    dArr[s++] = Double.parseDouble(ss);
                }

            }
            list.add(dArr);
        }
        int max = 0;
        for (int i = 0; i < list.size(); i++) {
            if (max < list.get(i).length)
                max = list.get(i).length;
        }
        double[][] array = new double[list.size()][max];
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < list.get(i).length; j++) {
                array[i][j] = list.get(i)[j];
            }
        }
        return array;
    }

2.FileInputStream实现读取文本数据，并保存为二维数组

private static double[][] getFileInput(String pathName) throws Exception {
        FileInputStream inputStream = null;
        Scanner sc = null;
        List<double[]> list = new ArrayList<>();
        inputStream = new FileInputStream(pathName);
        sc = new Scanner(inputStream, "utf-8");
        while (sc.hasNextLine()) {
            String line = sc.nextLine();
            int s = 0;
            String[] arr = line.split(",");
            double[] dArr = new double[arr.length];
            for (String ss : arr) {
                if (ss != null) {
                    dArr[s++] = Double.parseDouble(ss);
                }
            }
            list.add(dArr);
        }
        int max = 0;
        for (int i = 0; i < list.size(); i++) {
            if (max < list.get(i).length)
                max = list.get(i).length;
        }
        double[][] array = new double[list.size()][max];
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < list.get(i).length; j++) {
                array[i][j] = list.get(i)[j];
            }
        }
        inputStream.close();
        sc.close();
        return array;
    }