code: public static TerminalOp<Double, OptionalDouble> makeDouble(boolean mustFindFirst) {
          return new FindOp<>(mustFindFirst, StreamShape.DOUBLE_VALUE, OptionalDouble.empty(),
                              OptionalDouble::isPresent, FindSink.OfDouble::new);
      }
docs: Constructs a {@code FindOp} for streams of doubles.
  
  @param mustFindFirst whether the {@code TerminalOp} must produce the
  first element in the encounter order
  @return a {@code TerminalOp} implementing the find operation