code: public static boolean isFileInDirectory(File file, File directory) throws IOException {
          return (file.exists()
               && !file.isHidden()
               && directory.isDirectory()
               && file.getCanonicalPath().startsWith(directory.getCanonicalPath()));
      }
docs: Utility method to determine if a given file is located somewhere in the directory provided.
  
  @param file used to check if it is located in the provided directory.
  @param directory to validate whether or not the provided file resides.
  @return true if the file is somewhere in the provided directory, false if it is not.
  @throws IOException if the canonical path for either of the input directories can't be determined.