How to sort files from a directory by date in java?

Question

I have a method which reads the content from files located in a directory. But for functional reasons it is necessary to start with the oldest file (indicated by the property lastmodified) and end with the newest file.

This is the code how I open and read the files:

        FilenameFilter filter = new FilenameFilter() {
        public boolean accept(File dir, String name) {
            return name.matches("access_log.*");
        }
    };

    File folder = new File("/home/myfiles");
    File[] listOfFiles = folder.listFiles(filter);

    for (int i = 0; i < listOfFiles.length; i++) {
        String sFileName = listOfFiles[i].getName();
        File accessLogFile = new File(aLog.getPath(), sFileName);
        long time=accessLogFile.lastModified();
        // do something with the file
    }

Has anybody a solution how I can quickly sort my list of files by date?

Does http://stackoverflow.com/questions/203030/best-way-to-list-files-in-java-sorted-by-date-modified contain the answer to your question? — sverre, Jun 12 '11 at 07:05
Have you tried FileUtils.dirListByAscendingDate? http://www.rgagnon.com/javadetails/java-0606.html — excanoe, Jun 12 '11 at 07:05
You seem to be interested in log files. These are often named in a way such that lexical sorting by file name also sorts by time. — Ted Hopp, Jun 12 '11 at 07:05

score 39 · Accepted Answer · edited Aug 01 '21 at 08:38

39

Java 8

public static void sortOldestFilesFirst(File[] files) {
    Arrays.sort(files, Comparator.comparingLong(File::lastModified));
}

public static void sortNewestFilesFirst(File[] files) {
    Arrays.sort(files, Comparator.comparingLong(File::lastModified).reversed());
}

Java 7

public static void sortOldestFilesFirst(File[] files) {
    Arrays.sort(files, new Comparator<File>() {
        @Override
        public int compare(File a, File b) {
            return Long.compare(a.lastModified(), b.lastModified());
        }
    });
}

public static void sortNewestFilesFirst(File[] files) {
    Arrays.sort(files, new Comparator<File>() {
        @Override
        public int compare(File a, File b) {
            return Long.compare(b.lastModified(), a.lastModified());
        }
    });
}

edited Aug 01 '21 at 08:38

fredoverflow

246,999
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answered Jun 12 '11 at 08:50

javing

11,899
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2

Hi you could generify this which would mean you could remove the casting in the compare method: Arrays.sort( files, new Comparator(){...}) – Simon B Feb 03 '14 at 09:27
Thanks, dude! it still works! – oskarko Mar 13 '17 at 16:25
You made my day :) Thank you. – Pratik Butani May 14 '17 at 04:50
@PratikButani Glad you found it useful :) – javing May 14 '17 at 10:12
what is the use of -1, 1 and 0? – Benjamin G Sep 13 '17 at 08:32

score 3 · Answer 2 · edited May 23 '17 at 12:17

3

Your best option is to use a comparator. There is a similar question and answer here... Best way to list files in Java, sorted by Date Modified?

edited May 23 '17 at 12:17

Community

1
1

answered Jun 12 '11 at 07:05

Ben

1,525
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19

score 0 · Answer 3 · answered Jun 12 '11 at 07:05

0

I would use FileUtils in commons-io to get back the Collection of Files. I would then apply a custom comparator. It should be pretty easy.

answered Jun 12 '11 at 07:05

javamonkey79

17,217
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How to sort files from a directory by date in java?

3 Answers3

Java 8

Java 7

Linked