Похоже кривая сортировка в TreeMap

public void sort(){
        Comparator<File> comparator = new Comparator<File>() {
            @Override
            public int compare(File o1, File o2) {
                return o1.getName().compareToIgnoreCase(o2.getName());
            }
        };
        smallFiles.sort(comparator);
    }

public class Solution {

    private static TreeSet<File> set = new TreeSet<>();

    public static void main(String[] args) throws IOException {
        File path = new File(args[0]);
        File resultFileAbsolutePath = new File(args[1]);
        File allFilesContent = new File(resultFileAbsolutePath.getParent()+File.separator+"allFilesContent.txt");
        FileUtils.renameFile(resultFileAbsolutePath, allFilesContent);
        FileOutputStream fileOutputStream=new FileOutputStream(allFilesContent);

        fill(path.getPath());

        //записываем все файлы map в файл allFilesContent

        for (File filesss: set) {
            FileInputStream fileInputStream = new FileInputStream(filesss);
            while (fileInputStream.available()>0) {
                fileOutputStream.write(fileInputStream.read());
            }
                fileOutputStream.write("\n".getBytes());
                fileInputStream.close();
        }
        fileOutputStream.close();
    }

    private static void fill (String path){
        File files[]=new File(path).listFiles();
        for (File file:files) {
            if (file.isDirectory()){
            fill(file.getAbsolutePath());
            continue;
            }
        if (file.length()<=50){
                set.add(file);
            }
        }
    }
}