code: public boolean validateContent() throws IOException {
          if (checksum == null) {
              return false;
          }
  
          final FileInputStream fis = new FileInputStream(downloadedFile);
          final String computedHash = computeHashSHA256(fis);
  
          return computedHash.equals(checksum);
      }
docs: Validates the {@code downloadedFile}'s contents against a SHA-256
  checksum provided with it.
  
  @return {@code true} if the computed checksum matches {@code checksum},
  {@code false} if it does not match or if the {@code checksum} is
  {@code null}.
  @throws IOException Thrown if an IO error occurred while reading the
  {@link File downloadedFile}.