How to get oldest file in a directory using Java

Question

Are there any methods for obtaining the oldest file in a directory using java? I have a directory i write log files to and would like to delete log files after ive recorded over 500 log files (but only want to delete the oldest ones).

The only way i could conceive myself is:

Get the list of files using the File.listFiles() method
Loop through each File
Store the last modified date using File.lastModified() and compare with File from loop iteration, keep the oldest lastModified()

The inconvenient aspect of this logic is that i would have to loop the log directory every time i want to get the oldest files and that does not seem the most efficient.

i expected the java.io.File library would have a method to get the oldest file in a directory but it doesnt seem to exist, or i havent found it. If there is a method for obtaining the oldest file in a directory or a more convenient approach in programming the solution, i would love to know.

Thanks

This method that you wish to find, would have to do exactly the same, loop through all the files. — Yoda, Mar 25 '19 at 21:47
The Java logger can do rotating log files, relieving you of the need to keep track of this. See https://stackoverflow.com/questions/16522339/rolling-log-files-removing-old-log-files/16524062#16524062. (Actually every logging framework can, but I prefer not to rely on third party libraries if it’s not necessary.) — VGR, Mar 26 '19 at 02:27

Benji Weiss · Accepted Answer · 2019-06-28T23:38:04.863

Based off of @Yoda comment, i figured i would answer my own question.

public static void main(String[] args) throws IOException {
    File directory = new File("/logFiles");
    purgeLogFiles(directory);
}

public void purgeLogFiles(File logDir){
    File[] logFiles = logDir.listFiles();
    long oldestDate = Long.MAX_VALUE;
    File oldestFile = null;
    if( logFiles != null && logFiles.length >499){
        //delete oldest files after theres more than 500 log files
        for(File f: logFiles){
            if(f.lastModified() < oldestDate){
                oldestDate = f.lastModified();
                oldestFile = f;
            }               
        }

        if(oldestFile != null){
            oldestFile.delete();
        }
    }
}

I'm not sure you can pass a String into that method in your proposed solution. Probably meant to create a file object? — simgineer, Jun 28 '19 at 23:34

score 1 · Answer 2 · answered Mar 25 '19 at 22:05

Unfortunately, you're gonna have to just walk the filesystem. Something like:

public static void main(String[] args) throws IOException {
    String parentFolder = "/var/log";
    int numberOfOldestFilesToFind = 5;

    List<Path> oldestFiles = findOldestFiles(parentFolder, numberOfOldestFilesToFind);

    System.out.println(oldestFiles);
}

private static List<Path> findOldestFiles(String parentFolder, int numberOfOldestFilesToFind) throws IOException {
    Comparator<? super Path> lastModifiedComparator = 
            (p1, p2) -> Long.compare(p1.toFile().lastModified(),
                                     p2.toFile().lastModified());

    List<Path> oldestFiles = Collections.emptyList();

    try (Stream<Path> paths = Files.walk(Paths.get(parentFolder))) {
        oldestFiles = paths.filter(Files::isRegularFile)
                           .sorted(lastModifiedComparator)
                           .limit(numberOfOldestFilesToFind)
                           .collect(Collectors.toList());
    }

    return oldestFiles;
}

How to get oldest file in a directory using Java

2 Answers2