Question

private static List<Book> readDataFromCSV(String fileName) {    
    List<Book> books = new ArrayList<>();
    Path pathToFile = Paths.get(fileName);

    // create an instance of BufferedReader
    // using try with resource, Java 7 feature to close resources
    try (BufferedReader br = Files.newBufferedReader(pathToFile,
            StandardCharsets.US_ASCII)) {
        // read the first line from the text file
        String line = br.readLine();

        // loop until all lines are read
        while ((line  = br.readLine())!= null) {
            // use string.split to load a string array with the values from
            // each line of
            // the file, using a comma as the delimiter
            String[] attributes = line.split("\\|");

            Book book = createBook(attributes);

            // adding book into ArrayList
            books.add(book);

            // read next line before looping
            // if end of file reached, line would be null
            line = br.readLine();
        }

    } catch (IOException ioe) {
        ioe.printStackTrace();
    } 
    return books;
}


private static Book createBook(String[] metadata) { 
    String name = metadata[0];  
    String author = metadata[1]; // create and return book of this metadata 
    return new Book(name, price, author); 
}

上面的代码从文本文件（一个csv文件）中每隔第二行跳过一次。它提供备用行的数据，并使用Java 7语法。请提供一些建议，以解决问题或改进方法。

Answer 1

在br.readLine()条件内删除while，即

// read the first line from the text file
String line = br.readLine();
// loop until all lines are read
while (line != null)
{
    ...
    // read next line before looping
    // if end of file reached, line would be null
    line = br.readLine();
}

Answer 2

您已在循环中两次调用br.readLine（）函数。

一个条件为：

while((line = br.readLine()) != null)

第二个在循环的结尾。

因此，循环实际上是在末尾读取一行，然后在不处理的情况下从头开始读取下一行。为避免这种情况，您可以在循环末尾删除br.readLine。

while ((line  = br.readLine())!= null)
                {

                    // use string.split to load a string array with the values from
                    // each line of
                    // the file, using a comma as the delimiter
                   String[] attributes = line.split("\\|");

                   Book book = createBook(attributes);

                   // adding book into ArrayList
                   books.add(book);
               }

如果没有收到，条件：

while((line = br.readLine()) != null)

实际上正在执行以下操作：

将br.readLine（）的返回值存储在变量行中，

，然后检查条件。因此，您无需在循环中再次调用它。

从java中的csv文件读取时跳过行

2 个答案: