This trick has also been likened to a trout swimming up stream by my favourite comedy juggler Frank Olivier, so take your pick - Javelin or Trout (I know which one I'd rather catch).
The javelin is more a type of throw than an actual trick, it is quite similar to a floater in that the club is thrown without any spin, and travels from one hand to the other, but the grip used to throw it is different. Pick up a club and raise your hand up to your shoulder, with the body of the club pointing forward, as if it were a javelin about to be thrown. The throwing action is more of a lift straight upwards, with a slight forwards motion. Because the club starts off at head level rather than waist level as normal, you don't need to throw it up very far, just 6 inches or so, so that it peaks at the same height as the other throws. Hold the club right in the middle so that it won't spin too much after you throw it.
In order to get the club the right way round in your hand to do this trick, you should catch it as you will throw it - with your hand up by your shoulder, palm facing inwards, thumb at the back.:
The club's handle should fall into your hand, leaving you ready for the trick.. The trick looks better if you give the club a bit of an upwards tilt, so that it points along the path which it will follow through the air, as a javelin would.
Continuous javelin throws from one hand look really good.