code: public static boolean is100ContinueExpected(HttpMessage message) {
          return isExpectHeaderValid(message)
            // unquoted tokens in the expect header are case-insensitive, thus 100-continue is case insensitive
            && message.headers().contains(HttpHeaderNames.EXPECT, HttpHeaderValues.CONTINUE, true);
      }
docs: Returns {@code true} if and only if the specified message contains an expect header and the only expectation
  present is the 100-continue expectation. Note that this method returns {@code false} if the expect header is
  not valid for the message (e.g., the message is a response, or the version on the message is HTTP/1.0).
  
  @param message the message
  @return {@code true} if and only if the expectation 100-continue is present and it is the only expectation
  present