How can I sort files in a directory in java?

Question

Here is my code and it works ! But I want to be able to sort the files list according to name, size, modification date and more

import java.io.File;
import org.apache.commons.io.FileUtils;

public class StartingPoint {
    public static void main(String[] args) {
        File file = new File(
                "/home/t/lectures");
        File[] files = file.listFiles();
        for (File f : files) {
            System.out.println("File : " + f.getName() + " ["
                    + FileUtils.byteCountToDisplaySize(f.length()) + "]");
        }
    }
}

score 14 · Accepted Answer · edited Nov 25 '14 at 08:58

Arrays.sort( files, new Comparator<File>() {
    public int compare( File a, File b ) {
        // do your comparison here returning -1 if a is before b, 0 if same, 1 if a is after b
    }
} );

You could define a bunch of different Comparator classes to do different comparisons like such:

public class FileNameComparator implements Comparator<File> {
    public int compare( File a, File b ) {
        return a.getName().compareTo( b.getName() );
    }
}

public class FileSizeComparator implements Comparator<File> {
    public int compare( File a, File b ) {
        int aSize = a.getSize();
        int bSize = b.getSize();
        if ( aSize == bSize ) {
            return 0;
        }
        else {
            return Integer.compare(aSize, bSize);
        }
    }
}

...

Then you would just swap em out:

Arrays.sort( files, new FileNameComparator() );

or

Arrays.sort( files, new FileSizeComparator() );

@SergeyGazaryan, I didn't read it that way, but will modify my answer to include that. Thanks. — Lucas, Nov 12 '11 at 19:49
Perfect, it's easy to implement different types of sorting beyond this step. Thanks. — taabouzeid, Nov 12 '11 at 19:49

score 4 · Answer 2 · answered Jun 17 '15 at 13:41

Example in Java8 to sort by last modification time:

Path dir = Paths.get("./path/somewhere");

Stream<Path> sortedList = Files.list(dir)
    .filter(f -> Files.isDirectory(f) == false) // exclude directories
    .sorted((f1, f2) -> (int) (f1.toFile().lastModified() - f2.toFile().lastModified()));

then you may convert sortedList to Array or continue using lambda expressions with .forEach:

    .forEach(f -> {do something with f (f is Path)})

How can I sort files in a directory in java?

2 Answers2

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