code: public static synchronized List<Media> getByExtension(File jar, String fullPath, int prefixLength, String extension)
      {
          if (jar.isDirectory())
          {
              return UtilFile.getFilesByExtension(new File(jar, fullPath), extension)
                             .stream()
                             .map(file -> Medias.create(file.getName()))
                             .collect(Collectors.toList());
          }
          final Collection<ZipEntry> entries = UtilZip.getEntriesByExtension(jar, fullPath, extension);
          final List<Media> medias = new ArrayList<>(entries.size());
          for (final ZipEntry entry : entries)
          {
              final Media media = create(entry.getName().substring(prefixLength));
              medias.add(media);
          }
          return medias;
      }
docs: Get all media by extension found in the direct JAR path (does not search in sub folders).
  
  @param jar The JAR file (must not be <code>null</code>).
  @param fullPath The full path in JAR (must not be <code>null</code>).
  @param prefixLength The prefix length in JAR (must not be <code>null</code>).
  @param extension The extension without dot; eg: png (must not be <code>null</code>).
  @return The medias found.
  @throws LionEngineException If invalid parameters.