"Helpful NullPointerException" is a game changer. I haven’t tried it yet, but from the looks of it this seems to be a good enough reason to upgrade to Java 14 by itself.

Part I is here: https://java.christmas/2019/17

I wish they changed the spec so iterating over a null Iterable would not throw an NPE:

Iterable items = null;

for(Object x: items)

{

   // will not enter the loop

}