如何计算 Java 中某些列的 txt 文件中整数出现的次数？

Question

基本上是为了解释我有一个txt文档需要读取到文件http://m.uploadedit.com/bbtc/1515402294116.txt

我怎样才能专门计算第 3 列的数字？比如txt文档第3列的前10个数字是...

1, 1, 3, 3, 1, 1 ,1, 3, 1, 2

如果我要对值 3 进行计数，它将是：

"The number 3 occurs: 3 times"

但我有一个非常大的样本，我只想包含 3rd column 的这些值，有人能帮助我吗？我已经被这个问题困了一段时间了。我认为您必须在数组中设置每一列并以这种方式工作。

Answer 1

您的文本文件看起来像制表符分隔，您可以使用 BufferedReader 读取每一行并每次提取第三列。使用流可以轻松完成数字计数。

    File file = new File(PATH_TO_TXT);
    ArrayList<Integer> storage = new ArrayList<>();
    try (BufferedReader br = new BufferedReader(new FileReader(file))) {
        String line;
        while ((line = br.readLine()) != null) {
            String[] arr = line.split("\t");
            storage.add(Integer.valueOf(arr[2].trim()));
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    Map<Integer, Long> occurrences = storage.stream()
     .collect(Collectors.groupingBy(e -> e, Collectors.counting()));

Answer 2

如果每个值都由“,”分隔，您可以使用此代码：

BufferedReader br = null;
int counter = 0;
try {
    br = new BufferedReader(new FileReader("testfile.txt"));
    String line;
    // the column you want to get:
    int column = 3;
    // the value you want to search
    String value = "3";

    while ((line = br.readLine()) != null) {
        int first = 0;
        int last = line.indexOf(",");
        //get index of the column
        for (int i = 0; i < column - 1; i++) {
            first = last;
            last = line.indexOf(",", last + 1);
        }
        // get the value of the column
        String column3value = line.substring(first + 1, last);
        // counter +1 for every value
        if (column3value.equals(value)) {
            counter += 1;
        }
    }
    System.out.println(counter);
} catch (IOException e) {
    e.printStackTrace();

}

如何计算 Java 中某些列的 txt 文件中整数出现的次数？

How can I count the number of integer occurences from a txt file from certain columns in Java?

java

arrays

bufferedreader

readfile