Question

As a result of processing, some data files are written to disk.

• Count of files between 2 servers (MAC and Linux) match
• File names are identical between systems
• Files content is identical between systems, as measured by md5sum

Report is then computed based on content read from said files, using

    for (File f : contentDirectory.listFiles()) {
               // magic

.listFiles() javadoc says:

There is no guarantee that the name strings in the resulting array
will appear in any specific order; they are not, in particular,
guaranteed to appear in alphabetical order.

While that is true, i wonder … the order in which files will be listed, is not random, right? I mean, listing same files 2 times will produce the same results is this correct?

Does this mean that when files are listed on 2 different systems, order is likely to not be the same?

Ultimately the bigger question is, how to list files in a directory in same order regardless of OS file are stored on?

Answer 1

Just sort the files. File is comparable so we don’t even need a comparator:

File[] files = File.listRoots()[0].listFiles();
Arrays.sort(files);
System.out.println(Arrays.asList(files));

(This example simply takes the files from the first root directory, that should have some content on every computer ;))

Alternative

The file objects should be unique so we can create a tree set:

for (File file : new TreeSet<File>(Arrays.asList(contentDirectory.listFiles()))) {
    System.out.println(file.getName());  // replace with magic ;)
}