RFR(L): 8218628: Add detailed message to NullPointerException describing what is null.

[Langer, Christoph]

Hi Goetz,

> 91         synchronized (this) {
> -> I think this is not needed here. The transient modifier for
> lazyComputeMessage already implies the lock on the Object, I think.

please ignore this comment, I'm wrong here. I confused transient with volatile...

/Christoph