JVM GC and unused references

Question

Let's say there are following four objects in a Java program:

• main
• a
• b
• c

The dependencies are as follows:

main ==> a ==> b ==> c

In other words, main uses a , a uses b , b uses c .

Now, value of object a changes from reference to b to null . What it means is that there are no active references to b , making it available for garbage collection:

main ==> a =/=> b ==> c

What could happen now:

A) In laymans terms, b can be garbage collected at any time. My assumption is that c will become elligible for gargabe collection only after b is garbage collected.

B) However, I imagine this could be a case that JVM could somehow distinguish between references to c from GC-eligible and non-GC-eligible objects, and therefore mark c as eligible at the same time as b .

Is the behaviour determined by Java Language Specification, or any JVM-related specification? Or is it left for the JVM implementation to decide?

Answer 1

多亏有了此链接，我认为选项B才是正确的： https : //www.dynatrace.com/resources/ebooks/javabook/how-garbage-collection-works/一旦GC根不再可以访问b和c ，它们就可以了两者都可以同时收藏。