Abhilash -- Questions

[Swati Jambhale]

Hello Friends
Those question are from abhilash's collection.
Q1)A class which has all its constructors declared as private
1)Cannot be instantiated by any other class.
2)Cannot be extended.
3)Both i and ii.
4)has to be declared final.
ans : 3
I think question should be more specific, as one can instantiate such class in inner class defined in this class. What do you say?
Q2)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
ans is false? Do gc work differently in case of Threads ?

Swati

[bill bozeman]

For question 2, I can read that two ways.

One is stating that th has completed execution and is no longer accessible, so will it be eligble for garbage colletion.

If that is the case then I would say the answer is true.
However, you can also read it this way:

th has completed its excution. Because it has complted execution, it is no longer accessible, so it will be elgible for garbage collection.

I would say false here because just because the run method has completed, doesn't mean that you can no longer access it. You can not make it start() again, but you can still call other methods on it.
Question is a little too ambiguous.
Bill

[This message has been edited by bill bozeman (edited February 28, 2001).]

[nachiket deshpande]

i am not able to understand why a class with private constructors can not be extended?
please help

[bill bozeman]

It can't be extended because when you extend a class, the subclasses constructors call the construcors of the parent class. It either calls them directly, or it calls the default constructor. If the constructor is private, then it can't call the constructor, hence you can't extend it.
Bill

[dropinboy]

hi there
i'm as green as they come, but i think that if the constructors are private and the methods aren't static then extending the class won't be of much use since u can't use the methods without constructing an instance of the class, but constructors are private.
hope this helps

[dropinboy]

i prefer your answer Bill, the subclass's constructors implicitly call the super classes constructor unless u've explicitely called super();
more of my 2 cents };-)

[bill bozeman]

dropinboy,
Your name doesn't comply with our naming policy here at the ranch. Check out this link for more info, www.javaranch.com/name.jsp
Please re-register with a more appropriate name.
Thanks,

Bill