code: public static <T> TerminalOp<T, Optional<T>> makeRef(boolean mustFindFirst) {
          return new FindOp<>(mustFindFirst, StreamShape.REFERENCE, Optional.empty(),
                              Optional::isPresent, FindSink.OfRef::new);
      }
docs: Constructs a {@code TerminalOp} for streams of objects.
  
  @param <T> the type of elements of the stream
  @param mustFindFirst whether the {@code TerminalOp} must produce the
  first element in the encounter order
  @return a {@code TerminalOp} implementing the find operation