questions on Thread

[mark stone]

found this in a mock test lease answer the 3 questions
A demon Thread group
1 has only demon threads.
2 can have non demon threads.
3 does not exist after all non demon threads in the group have finished executing.
4 does not exist after all the threads in the group have finished executing.
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Assume that th is an instance holding a thread object. th.start() causes the thread to start running and eventually complete its execution. The object reference by th is not accessable any more and is garbage collected when the garbage collecter runs.
True
False
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A class has 2 synchronized methods, one being static and other non-static.
which one is correct:
The class wide lock and the instance lock being independent of each other.
The class wide lock and the instance lock being mutually exclusive.
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[Rob Ross]

Originally posted by mark stone:
A demon Thread group
1 has only demon threads.
2 can have non demon threads.
3 does not exist after all non demon threads in the group have finished executing.
4 does not exist after all the threads in the group have finished executing.
Answer :4
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Assume that th is an instance holding a thread object. th.start() causes the thread to start running and eventually complete its execution. The object reference by th is not accessable any more and is garbage collected when the garbage collecter runs.
True
False
Answer :False
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A class has 2 synchronized methods, one being static and other non-static.
which one is correct:

The class wide lock and the instance lock being independent of each other.
The class wide lock and the instance lock being mutually exclusive.
----------------------------------------------

[ January 24, 2002: Message edited by: Rob Ross ]

[mark stone]

why is the answer false ?

Assume that th is an instance holding a thread object. th.start() causes the thread to start running and eventually complete its execution. The object reference by th is not accessable any more and is garbage collected when the garbage collecter runs.
True
False
Answer :False

Originally posted by Rob Ross:

[ January 24, 2002: Message edited by: Rob Ross ]

[Rick Reumann]

Originally posted by mark stone:

A class has 2 synchronized methods, one being static and other non-static.
which one is correct:
The class wide lock and the instance lock being independent of each other.
The class wide lock and the instance lock being mutually exclusive.

I remember that above question coming up on JWhiz and was confused how the two answers are really that different? Aren't the two locks independent of each other which also means they are mutually exclusive? (Also, should the word "being" be replaced with "are" ?)

[Rob Ross]

Mark, if I make a thread...

Thread th = new Thread();
then start the thread...

th.start();
and the thread runs to completion, the thread is dead, but th still contains a reference to the thread. Until you set th to null, this thread object still has a reference to it.
When you write
th = null;
then and only then will the thread above be eligible for garbage collection.

Rob

[Paul Salerno]

A class has 2 synchronized methods, one being static and other non-static.
which one is correct:
The class wide lock and the instance lock being independent of each other.
The class wide lock and the instance lock being mutually exclusive.

Seems very ambiguous I've heard of Object Lock never any "class wide lock" or "instance lock". Is this sort of thing a possiblity on the exam?