[scjp exam] garbage collection questions

can someone please post me some garbage collection questions + correct answers, because i've taken the SCJP test again and i didn't passed it again. A co-worker of mine also didn't passed either.
(We both got 0% on Garbage Collection every time) And i really thought i had it correct the last time.
So please can someone mail/post me some garbage collection questions? thanks!

The garbage collector collects unreachable objects.
You have no control over when the objects are
collected, but there is a guarantee that all
unreachable objects will be collected before an
OutOfMemoryError is thorwn.Exactly my thoughts...
That's it. It really is just that simple. I scored 94%
on the Programmer's Exam, with 100% in the garbage
collection section.Hmm i got 54% last exam i took. I really begin to doubt about myself, because i find the questions on the exam so tricky.. Last book was Exam Cram (Java), and i found this a very nice and good book to study for the exam. Garbage collection is just one question, so it's either 0% or 100%. So far it hasn't gone anything higher then 0% with me.
Here are some questions:
1. When is the Object first available for garbage
collection (when does it become unreachable)?
Object o = new Object();
Object p = o;
o = null;
p = null;p = null; -> available for gc.
2. When is the Object first available for garbage
collection?
Object o = new Object();
Vector v = new Vector();
v.add(o);
o = null;
v = null;v = null; -> available for gc.
3. Can the Vectors be garbage collected at the end of
this code?
Vector v = new Vector();
Vector w = new Vector();
v.add(w);
w.add(v);
v = null;
w = null;yes
Now i have a question:
public int foo {
Integer result = new Integer(10);
result = null;
return result;
when is result available for gc?

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    [Sun Oct 22 01:21:38 2006][22855][memory ] 120439.582: nursery GC 409986K->345832K (786432K), 153.534 ms
    [Sun Oct 22 01:21:42 2006][22855][memory ] 120443.544: nursery GC 410632K->346473K (786432K), 121.371 ms
    [Sun Oct 22 01:21:44 2006][22855][memory ] 120445.508: nursery GC 411273K->347591K (786432K), 60.688 ms
    [Sun Oct 22 01:21:44 2006][22855][memory ] 120445.623: nursery GC 412391K->347785K (786432K), 68.935 ms
    [Sun Oct 22 01:21:45 2006][22855][memory ] 120446.576: nursery GC 412585K->348897K (786432K), 152.333 ms
    [Sun Oct 22 01:21:45 2006][22855][memory ] 120446.783: nursery GC 413697K->349080K (786432K), 70.456 ms
    [Sun Oct 22 01:34:16 2006][22855][memory ] 121197.612: nursery GC 437378K->383392K (786432K), 165.771 ms
    [Sun Oct 22 01:37:37 2006][22855][memory ] 121398.496: nursery GC 469709K->409076K (786432K), 78.257 ms
    [Sun Oct 22 01:37:37 2006][22855][memory ] 121398.730: nursery GC 502490K->437713K (786432K), 65.747 ms
    [Sun Oct 22 01:44:03 2006][22855][memory ] 121785.259: nursery GC 536605K->478156K (786432K), 132.293 ms
    [Sun Oct 22 01:44:04 2006][22855][memory ] 121785.603: nursery GC 568408K->503635K (786432K), 71.751 ms
    [Sun Oct 22 01:50:39 2006][22855][memory ] 122180.985: nursery GC 591332K->530811K (786432K), 131.831 ms
    [Sun Oct 22 02:13:52 2006][22855][memory ] 123573.719: nursery GC 655566K->595257K (786432K), 117.311 ms
    [Sun Oct 22 02:36:04 2006][22855][memory ] 124905.507: nursery GC 688896K->632129K (786432K), 346.990 ms
    [Sun Oct 22 02:50:24 2006][22855][memory ] 125765.715-125765.904: GC 786032K->143954K (786432K), 189.000 ms
    [Sun Oct 22 02:50:26 2006][22855][memory ] 125767.535-125767.761: GC 723232K->70948K (786432K), 225.000 ms
    vvvvv
    [Sun Oct 22 02:50:27 2006][22855][memory ] 125768.751-125768.817: GC 712032K->71390K (786432K), 64.919 ms
    [Sun Oct 22 02:50:28 2006][22855][memory ] 125769.516-125769.698: GC 711632K->61175K (786432K), 182.000 ms
    [Sun Oct 22 02:50:29 2006][22855][memory ] 125770.753-125770.880: GC 709632K->81558K (786432K), 126.000 ms
    [Sun Oct 22 02:50:30 2006][22855][memory ] 125771.699-125771.878: GC 708432K->61368K (786432K), 179.000 ms
    So, I'm running with the default GC strategy which lets the GC pick the most suitable approach (single space or generational). It seems to switch to generational almost immediately and runs well - most GC runs are in the nursery, and only once in a while it goes through the older space.
    Now, if you look at [Sun Oct 22 02:50:27 2006], that's when everything changes. GC starts running every second (later on it's running 3 times a second) doing huge sweeps. It never goes through the nursery again, although the strategy is still generational.
    It's all downhill from this point on, and it's a matter of hours (maybe a day) before we restart the server.
    I guess my only question is: What would cause such GC behavior?
    I would appreciate your ideas/comments!
    Thanks,
    Tenyo

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