When an object is first created (A), it is reachable and unfinalized.
As references to an object are discarded during program execution, an object that was reachable may become finalizer-reachable (B, C, D) or unreachable (E, F). (Note that a finalizer-reachable object never becomes unreachable directly; it becomes reachable when the finalizer from which it can be reached is invoked, as explained below.)
If the Java virtual machine detects that an unfinalized object has become finalizer-reachable or unreachable, it may label the object finalizable (G, H); moreover, if the object was unreachable, it becomes finalizer-reachable (H).
If the Java virtual machine detects that a finalized object has become unreachable, it may reclaim the storage occupied by the object because the object will never again become reachable (I).
At any time, a Java virtual machine may take any finalizable object, label it finalized, and then invoke its finalize method in some thread. This causes the object to become finalized and reachable (J, K), and it also may cause other objects that were finalizer-reachable to become reachable again (L, M, N).
A finalizable object cannot also be unreachable; it can be reached because its finalizer may eventually be invoked, whereupon the thread running the finalizer will have access to the object, as this (�15.8.3). Thus, there are actually only eight possible states for an object.
After an object has been finalized, no further action is taken until the automatic storage management determines that it is unreachable. Because of the way that an object progresses from the unfinalized state through the finalizable state to the finalized state, the finalize method is never automatically invoked more than once by a Java virtual machine for each object, even if the object is again made reachable after it has been finalized.
Explicit invocation of a finalizer ignores the current state of the object and does not change the state of the object from unfinalized or finalizable to finalized.
If a class does not override method finalize of class Object (or overrides it in only a trivial way, as described above), then if instances of such a class become unreachable, they may be discarded immediately rather than made to await a second determination that they have become unreachable. This strategy is indicated by the dashed arrow (O) in the transition diagram.
Above wordings from "JLS 2" 12.6
From above I think object have also "states", which are "Unfinalized", "Finalizer-reachable", "Finalizable" and "Finalized". It's ok to have this concept but my question is that whether or not this concept is included in SCJP2 certification?
Regards
Farhan
