asked on

Java Exception

I am a bit confused bu exception.

For example:

(not real code)

try
{
sth.domethod();
print 1;
}

catch (exception a)
{
print 2;
}

catch (exception b)
{
print 3
}

finallu
{
print 4
}

print 5

if there is an expcetion c in sth.domethod(), which is not caught by a or b, will the program print
4
or
45

?

If there is no exception, will it print
145
or
14?

In other words, in which case will the program execute the "print 5" after finally clause and in which case it does not.

Thanks

BogoJoker

Hi tiger0516,

Finnally always prints, no matter if an exception is thrown or not.

If an exception is thrown, it will only print the first time it is caught. Then as it should, it will always print the finally.

If your first catch was catch (Exception a) print 2, then the only thing that would ever print would be 2 (if there was an exception). This is because all Exceptions extend Exception, so even if it was an IOException or a NullPointerException, they are both of type Exception, and that print 2 block will work, ignoring ALL the other catch statements.
Then finnaly it would print 4.

So a general rule is to always catch the most specific Exceptions first! =)

Joe P

SOLUTION

fargo

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fargo

Sorry BogoJoker, same timing.

BogoJoker

No problem, the fact we both agree is comforting to me and hopefully evidence to tiger that we are both right.
For us both answering the question in 5 minutes, that is a good thing too =)

Joe P

tiger0516

ASKER

Hi Joe, thanks.

Back to my question,

question 1:

if there is another type expcetion,called c in sth.domethod() (my catch clauses, a and b, fails to catach c. in other words, c is an exception which is not a sub/super class of a or b), will the program print

4 or 45 ?

question 2:

If there is no exception at all, will it print
145 or 14?

I think it should be 145.

question 3:

in which case will the program execute after the finally clause and in which case it won't (simply terminate after the finally clause).

Thanks

BogoJoker

4 should always print
5 should always print
of course if your program goes into an infinite loop, or crashes, then there is a possibility that neither of these will print =)

The finnaly print 4 has 0 affect on the print 5 after the try catch.

Joe P

tiger0516

ASKER

>5 should always print

So you mean, assuming exception c is a subclass of neither exception a nor exception b, the output of the code if domethod() throws an exception c will be

45 ?

>The finnaly print 4 has 0 affect on the print 5 after the try catch.

So you mean the try-catch-finally mechanism is only good for the try-catch-finally segament? after the finally clause, the code will continue to run anyway?

Many thanks.

BogoJoker

Exactly!

All Goes Well: 145
doMethod throws exception a: 245
doMethod throws exception b: 345
doMethod throws exception c: program will crash if not handled, expect no output

Joe P

ASKER CERTIFIED SOLUTION

BogoJoker

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tiger0516

ASKER

Thanks a lot. I feel I now understand much more than a few hours ago :)

BogoJoker

Sure =)

Joe P