DirectoryStream返回路径的顺序如何？ 文件名，最后修改，文件大小？

Question

I am trying to read multiple files in a folder using DirectoryStream. There are 10 items altogether.

doc_01.txt, doc_02.txt, doc_03.txt, doc_04.txt, doc_05.txt, doc_06.txt, doc_07.txt, doc_08.txt, doc_09.txt, doc_10.txt

I wanted the file to be read in the order of their filename. Does DirectoryStream read the file in order of their filename? Because this is the result I get:

./mydata/doc_01.txt, ./mydata/doc_02.txt, ./mydata/doc_03.txt, ./mydata/doc_04.txt, ./mydata/doc_08.txt, ./mydata/doc_07.txt, ./mydata/doc_09.txt, ./mydata/doc_10.txt, ./mydata/doc_05.txt, ./mydata/doc_06.txt

This is my code:

public static void readData(){
    Instant start = Instant.now();
    System.out.println("Start reading");

    Path path = Paths.get(String.join(File.separator, ".", "mydata"));

    try(DirectoryStream<Path> stream = 
            Files.newDirectoryStream(path, "*.txt")
    ){
        for(Path entry : stream){
            System.out.println("reading: " +entry.toString());
        }
    }catch(IOException e){
        System.err.println("Error: " + e.getMessage());
        e.printStackTrace();
    }
    Instant end = Instant.now();
    System.out.println("Done in " + Duration.between(start, end).toString());
}

Answer 1

The javadoc of class DirectoryStream explicitly says:

The elements returned by the iterator are in no specific order . Some file systems maintain special links to the directory itself and the directory's parent directory. Entries representing these links are not returned by the iterator.

So, if you need a specific order, it's up to you to sort the Path s. For example, for an alphabetical sorting you can do like this:

DirectoryStream<Path> stream = ...;
List<Path> list = new ArrayList<>();
stream.forEach(list::add);
list.sort(Comparator.comparing(Path::toString));
for (Path entry: list) {
  System.out.println("reading: " +entry);
}