Java's new Z Garbage Collector (ZGC) is very exciting
(www.opsian.com)
ZGC restricts itself to 4Tb heaps which require 42-bits, leaving 22-bits of possible state of which it currently uses 4-bits: finalizable, remap, mark0 and mark1.
喔喔,4TB 耶!
不過可能也沒機會用到這麼多 ram ...