How do I sort results of File.listFiles() by creation date?

Question

In Java Sort how do I sort results of File.listFiles() by creation date?

I did have:

files = reportFolder.listFiles(new ReportFolderFilter()));
Collections.reverse(files);

But this will only sort them in reverse alphabetical order not creation date.

I would like a solution that does not rely on Apache Commons.

Possible duplicate of [java : Sort Files based on Creation Date](https://stackoverflow.com/questions/10249822/java-sort-files-based-on-creation-date) — Vasan, Apr 04 '18 at 19:38
You seem using File (java.io) and not Path (java.nio). `nio2` tag refers to `java.nio` — davidxxx, Apr 04 '18 at 19:42
@davidxxx i use both, just thought an answer using nio2 would be more likley — Paul Taylor, Apr 04 '18 at 20:00
I think you need to take a closer look at the duplicate question. There is a version of it using Apache but the main question pretty much gives what you need - it doesn't use any libs. — Vasan, Apr 04 '18 at 20:00

score 2 · Accepted Answer · edited Apr 05 '18 at 06:03

2

you can use Collections.sort or Arrays.sort or List.sort

You can get the creation date of a file by using java nio Files. readAttributes()

Arrays.sort(files, new Comparator<File>() {
        @Override
        public int compare(final File o1, final File o2) {
            try {
                BasicFileAttributes f1Attr = Files.readAttributes(Paths.get(f1.toURI()), BasicFileAttributes.class);
                BasicFileAttributes f2Attr = Files.readAttributes(Paths.get(f2.toURI()), BasicFileAttributes.class);
                return f1Attr.creationTime().compareTo(f2Attr.creationTime());
            } catch (IOException e) {
                return 0;
            }
        }
    });

Or using Comparator.comparing:

Comparator<File> comparator = Comparator.comparing(file -> {
    try {
        return Files.readAttributes(Paths.get(file.toURI()), BasicFileAttributes.class).creationTime();
    } catch (IOException e) {
        return null;
    }
});

Arrays.sort(files, comparator);

edited Apr 05 '18 at 06:03

ZhekaKozlov

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answered Apr 04 '18 at 19:41

niekname

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thx, but would be great if you actually add the creationDate logic. – Paul Taylor Apr 04 '18 at 19:55
listFiles returns an array. This answer isn't valid as is. – Vasan Apr 04 '18 at 20:01
I know, it is an example of how it should be implemented. In my example 'files' is not defined, so it could be a List :) Either way, you can simply convert the File[] to a list by using Arrays.asList(files) – niekname Apr 05 '18 at 04:58
1

`Comparator.comparing` would be much better here – ZhekaKozlov Apr 05 '18 at 05:34
true, I have also added this option – niekname Apr 05 '18 at 05:49
@ZhekaKozlov thanks Comparator.comparating works for me. – Paul Taylor Apr 05 '18 at 09:03

How do I sort results of File.listFiles() by creation date?

1 Answers1