最近在看Thinking in Java, 讀到How a garbage collector works 這一節的時候有這么幾句話不太理解 (前面講到一種簡單但是很慢的垃圾回收的方法是reference counnting) The garbage collector moves through the entire list of objects, andwhen it finds one with a reference count of zero it releases thatstorage (however, reference counting schemes often release an objectas soon as the count goes to zero). The one drawback is that ifobjects circularly refer to each other they can have nonzero referencecounts while still being garbage. 這是原文, 我不能理解的是為什么出現循環引用的時候他會出現仍然進行垃圾收集,因為循環引用的時候不應該是兩個object的counter都到不了0才對嘛,按照正常邏輯這兩個object出現的問題應該是永遠也不會被垃圾回收,而按照作者的意思恰好相反.