What triggers the java Garbage Collector

Question

I am a little confused to how garbage collection in Java works.

I get that an object becomes eligible for garbage collection when there are no more live references to it

Answer 1

The GC knows which objects are alive because it copies all live objects to a new memory area and all that are not copied are overwritten the next time.

Note that this is valid for current implementations of the GC in the Oracle VM. Other VMs could handle it another way.