code: String packageName(File file) {
          String path = file.getAbsolutePath();
          int begin = path.lastIndexOf(File.separatorChar + "com" + File.separatorChar);
          String packagePath = path.substring(begin + 1, path.lastIndexOf(File.separatorChar));
          String packageName =  packagePath.replace(File.separatorChar, '.');
          return packageName;
      }
docs: Retrieve package part of given file object.