private String getFileExtension(String fileName) {
        String fileNameArray[] = fileName.split("\\.");
        return fileNameArray[fileNameArray.length - 1];
    }
Resolves the file extension for the specified file.

@param fileName The name of the file (including its extension).
@return The extension of the file (excluding the dot ".").
core/src/main/java/com/filebrowser/FileBrowserEngine/FileBrowserEngine.java