constructors and exception handling

[Angus Parvis]

Hi,

When a method throws an exception, i always have to deal with it in some
way (let it fall through or catch it).
But when a constructor throws an exception, it does not have to be
caught. Why that?

I'm curious about the answer

Greetings,

Angus

 

[Tor Iver Wilhelmsen]

But when a constructor throws an exception, it does not have to be
caught. Why that?

It does (example: java.net.URL). Why do you think it doesn't have to?
Do you have an example?

Remember that RuntimeException and its subclasses need to be caught
even if you declare them in "throws".

 

[Angus Parvis]

It does (example: java.net.URL). Why do you think it doesn't have to?
Do you have an example?

I've tried it with java.net.URL and you're right. Uhm, maybe I've
confused something. But the code that made me think this is at home, not
here at work. I'll have a closer look and post my results

 

[Sebastian Scheid]

Hi,

It does (example: java.net.URL). Why do you think it doesn't have to?
Do you have an example?

Remember that RuntimeException and its subclasses need to be caught
even if you declare them in "throws".

That's wrong.
It's the other way around: a method doesn't need to declare a
RuntimeException to be thrown even if it does not catch it itself. Probably
Angus throws a RuntimeException in the constructor.

Sebastian

 

[Tor Iver Wilhelmsen]

That's wrong.

Yes, I think I was a bit tired when I wrote it: Runtime exceptions
need NOT be caught, even if you declare them in "throws".

 

[Angus Parvis]

That's wrong.
It's the other way around: a method doesn't need to declare a
RuntimeException to be thrown even if it does not catch it itself. Probably
Angus throws a RuntimeException in the constructor.

Sebastian

No, I always subclass java.lang.Exception. Not for a special reason, I
simply didn't know that a java.lang.RuntimeException does have to be
caught or declared to be thrown. But maybe at that point I used some
sublass of RuntimeException.

That's what the API Doc says:

"A method is not required to declare in its throws clause any subclasses
of RuntimeException that might be thrown during the execution of the
method but not caught."

I have to say, I don't like this - I'd say, that it's always better to
be aware of the exceptions that can be thrown and to handle them
appropriately.
What's your opinion? Any hints, in what cases it is better to throw a
subclass of RuntimeException and in what cases subclasses of Exception?

Angus

 

[Tor Iver Wilhelmsen]

I have to say, I don't like this - I'd say, that it's always better to
be aware of the exceptions that can be thrown and to handle them
appropriately.

Then you will hate C#, where ALL exceptions are like Java's
RuntimeExceptions. No checked exceptions.

 

[Angus Parvis]

Then you will hate C#, where ALL exceptions are like Java's
RuntimeExceptions. No checked exceptions.

I heard of that. What a nightmare .

 

[Roedy Green]

I heard of that. What a nightmare .

Oh, no, I am responsible. See

http://mindprod.com/unmainobfuscation.html

point 17.