code: public final DataHasher addData(File file, int bufferSize) {
          Util.notNull(file, "File");
          FileInputStream inStream = null;
          try {
              inStream = new FileInputStream(file);
              return addData(inStream, bufferSize);
          } catch (FileNotFoundException e) {
              throw new IllegalArgumentException("File not found, when calculating data hash", e);
          } finally {
              Util.closeQuietly(inStream);
          }
      }
docs: Adds data to the digest using the specified file, starting at the offset 0.
  
  @param file       input file.
  @param bufferSize size of buffer for reading data.
  
  @return The same {@link DataHasher} object for chaining calls.
  
  @throws HashException        when hash calculation fails.
  @throws NullPointerException when input file is null.