Looks like the previous commit is completely useless:

I used Calipher to compare getBlockChange(int) and getBlockChange(int,
BlockChange), and on a modern JVM it's actually slower to recylce the
object:
 0% Scenario{vm=java, trial=0, benchmark=Normal} 2,87 ns; ?=0,02 ns @ 3
trials 50% Scenario{vm=java, trial=0, benchmark=Recycle} 3,33 ns; ?=0,23
ns @ 10 trials

benchmark   ns linear runtime
   Normal 2,87 =========================
  Recycle 3,33 ==============================

So we'll revert it.