Comment by marginalia_nu

Nope, see for example "Custom 1":

  var buffer = ByteBuffer.allocate(4096);
  try (var fc = (FileChannel) Files.newByteChannel(tempFile, 
                        StandardOpenOption.READ)) 
  {

    buffer.flip();

    for (int i = 0; i < records; i++) {

        if (buffer.remaining() < 32) {
            buffer.compact();
            fc.read(buffer);
            buffer.flip();
        }

        int len = buffer.get();
        byte[] cityBytes = new byte[len];
        buffer.get(cityBytes);
        String city = new String(cityBytes);
        int temperature = buffer.getShort();

        stats.computeIfAbsent(city, k -> new ResultsObserver())
             .observe(temperature / 100.);
    }
  }