Question on layer/peeling

[Brian Goetz]

> By the way, C# solves this by having TryGet type of methods that return a
> boolean indicating success (I.e. found mapping) and set an out parameter to
> the value found.  You'd need a lightweight tuple or multi return to do the
> same in java,  I think.

Right, there's two ways to fix get():
  - Using the getOrDefault(key, sentinel) // added in Java 8
  - Using some sort of optional-like return type

Not quite at that part of the road yet.