Question

我从.csv文件中读取以“;”分隔的字段分号。我写了一些例外书来处理可能的偏差。但是，如果有异常，NetBeans会在最后一行之前读出错误消息。

这是输出的样子：

我不明白代码中的后一行如何能过时地打印出来。这是我的整个代码：

public static void reader(String fileName) throws IOException {
    try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
        String line;
        List<String> lineHolder = new ArrayList<>();
        StringTokenizer divider;
        String formatter = "%2s|%-30s|%-30s|%10s|%n";

        String separator = "----------";
        System.out.format("ID|%-30s|%-30s|birth date|%n", "name", "email");
        System.out.print("--+" + separator + separator + separator 
                + "+" + separator + separator + separator + "+" 
                + separator + "+\n");

        while ((line = br.readLine()) != null){
            if (line.startsWith("#", 0))
                continue;
            if (!line.contains(";")) {
                throw new IOException("too less data or not proper delimiter");
            }
            divider = new StringTokenizer(line, ";");
            lineHolder = arrayFiller(divider);
            dataChecker(lineHolder, line);
            System.out.format(formatter, lineHolder.get(0), lineHolder.get(1)
                , lineHolder.get(2), lineHolder.get(3));
        }
    } catch (FileNotFoundException ex) {
        System.err.println("The file not found.");
    } catch (IOException ex){
        System.err.println(ex.getMessage());
    }
    System.out.print("\n");
}

public static ArrayList<String> arrayFiller(StringTokenizer divider) {
    ArrayList<String> lineHolder = new ArrayList<>();
    while (divider.hasMoreTokens()) {
        lineHolder.add(divider.nextToken());
    }
    return lineHolder;
}

这些是例外：

public static void dataChecker(List<String> lineHolder, String line) throws IOException {
    if (lineHolder.size() < 4) {
        throw new IOException("too less data or not proper delimiter");
    } else if (lineHolder.size() > 4) {
        throw new IOException("too much data");
    } else if (lineHolder.get(0).length() > 2 
            || !Pattern.matches("[0-9]+", lineHolder.get(0))) {
        throw new IOException("Error during reading the file: "
                + "not proper ID field format");
    } else if (lineHolder.get(1).length() > 30 
            || !Pattern.matches("[a-zA-ZíÍöÖüÜóÓőŐúÚűŰáÁéÉ. ]+", lineHolder.get(1))) {
        throw new IOException("Error during reading the file: "
                + "not proper Name field format");
    } else if (lineHolder.get(2).length() > 30 
            || !Pattern.matches("[a-zA-Z0-9@. ]+", lineHolder.get(2))) {
        throw new IOException("Error during reading the file: "
                + "not proper Email field format");
    } else if (lineHolder.get(3).length() > 10 || dateFormatter(lineHolder.get(3))) {
        throw new IOException("Error during reading the file: "
                + "not proper Birth date field format");
    } 
}

public static boolean dateFormatter(String datum) {
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    try {
        LocalDate changedDate = LocalDate.parse(datum, dtf);
        return false;
    } catch (DateTimeParseException ex) {
        return true;
    }
}

和源文件：

#ID;name;email;birth date
1,Jakob George,gipszjakab@gmail.com,1981-11-23
2;Susan Smith;usa@gmail.com;1982-12-01
3;Poul Drake;gameover@gmail.com;1990-01-02
4;Isaac Wheather;ruck%sack@freemail.hu;1988-01-22
5;George T. Benson;bigman@hotmail.com;1977-08-12

我试图将方法（异常持有者）放入reader()方法中，但结果仍然相同。这怎么可能？我做错了什么？

Answer 1

错误消息是通过不同的输出流打印的。标准输出流NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kafka-service NodePort 10.99.113.234 <none> 32400:32400/TCP 6m34s kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 27d my-confluent-oss-cp-kafka ClusterIP 10.100.156.108 <none> 9092/TCP 102m my-confluent-oss-cp-kafka-connect ClusterIP 10.99.78.89 <none> 8083/TCP 102m my-confluent-oss-cp-kafka-headless ClusterIP None <none> 9092/TCP 102m my-confluent-oss-cp-kafka-rest ClusterIP 10.100.152.109 <none> 8082/TCP 102m my-confluent-oss-cp-ksql-server ClusterIP 10.96.249.202 <none> 8088/TCP 102m my-confluent-oss-cp-schema-registry ClusterIP 10.109.27.45 <none> 8081/TCP 102m my-confluent-oss-cp-zookeeper ClusterIP 10.102.182.90 <none> 2181/TCP 102m my-confluent-oss-cp-zookeeper-headless ClusterIP None <none> 2888/TCP,3888/TCP 102m schema-registry-service NodePort 10.103.100.64 <none> 32500:32500/TCP 33m zookeeper-np NodePort 10.98.180.130 <none> 32181:32181/TCP 53m用于正常的日志记录/输出，错误（通过System.err.println）转到stdout。您的控制台/终端会同时显示两者，但它们不会彼此等待完成打印内容。

编辑：也许this也有帮助。

EDIT2：如果您将错误更改为打印到文件，则将丢失控制台/终端中的错误输出。但是，也许对您来说还好吗？像这样：

stderr

如果要在控制台/终端上打印两者错误和标准输出，则由于每条印刷线都是独立的操作，因此无法控制两个流的时序。

Answer 2

    String separator = "----------";
    System.out.format("ID|%-30s|%-30s|birth date|%n", "name", "email");
    System.out.print("--+" + separator + separator + separator 
            + "+" + separator + separator + separator + "+" 
            + separator + "+\n");
    System.out.flush();
    while ((line = br.readLine()) != null)

由于System.out和System.err来自不同的输出流，因此它们不会彼此等待完成。在print语句之后立即清除缓冲区内存即可解决此问题。

异常消息如何超过已执行的打印行

2 个答案: