Here's an example of how to use the PathVisitorFileFilter class from the Apache Commons IO library to filter files based on the traversal of a directory:

import java.io.File;
import org.apache.commons.io.filefilter.PathVisitorFileFilter;

public class Main {
    public static void main(String[] args) {
        File dir = new File("/path/to/directory");

        // Create the filter that will visit the path
        PathVisitorFileFilter visitor = new PathVisitorFileFilter(new MyPathVisitor());

        File[] matchingFiles = dir.listFiles(visitor);

        for (File file : matchingFiles) {
            System.out.println(file.getName());
        }
    }

    private static class MyPathVisitor extends SimpleFileVisitor<Path> {

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
            if (file.toString().endsWith(".txt")) {
                return FileVisitResult.CONTINUE;
            }
            return FileVisitResult.SKIP_SUBTREE;
        }
    }
}

In this example, /path/to/directory should be replaced with the path to the directory you want to search through. The listFiles method is called on the dir object, and it takes an instance of PathVisitorFileFilter as an argument. The PathVisitorFileFilter constructor takes a PathVisitor as an argument. A PathVisitor is a class that implements the SimpleFileVisitor interface from the java.nio.file package. This class, MyPathVisitor in this case, allows to apply custom logic to traverse the file tree. In this example the visitor will continue the traversal if the file ends with .txt, otherwise it will skip that subtree. The filtered matching files are stored in the matchingFiles array, and their names are printed out using a for loop.

You can use any other logic to traverse and filter the files, for example you can use the visitFileFailed method to filter files that cannot be accessed and the preVisitDirectory method to filter directories that match certain criteria.

This filter allows to filter files based on the traversal of the directory, it will traverse the directory and its subdirectories, applying the logic implemented in the visitor class, this way it can filter files based on different criteria like file attributes, file type and so on.