Comments on: A Tale of Bad Exception Handling in Finally Blocks in Java

By: Basil Vandegriend

Basil Vandegriend — Thu, 17 Nov 2011 04:18:10 +0000

@dayDreamer if #7 (caught) is referring to catching the exception raised in #6, then you are right in how it would work. If you are expecting #7 to catch the exception from #1, I don’t believe it will, as exception #1 was not thrown within the scope of the #4/#5 try…catch block.

But it is easy to write a simple test and see what will happen, like I did in my article. No need to take my word for it :)

By: dayDreamer

dayDreamer — Sat, 29 Oct 2011 18:53:06 +0000

Hello,
I understood your solution for Abhisheks question..but what is wrong in saying this…
Lets have a step-by-step execution.
1.RuntimeException thrown
2.no catch statement,so it is still waiting for someone to catch
3.finally encountered. (still exception not caught)
4.it has a try and catch block.
5.catch(Exception e) waiting for an exception if any.
6.An uncaught exception found.(Maybe he found somewhere in buffer or so..)
7.caught!!
8.finish

At what point am i wrong?
Thanks.

By: Basil Vandegriend

Basil Vandegriend — Sun, 31 Jul 2011 04:56:18 +0000

Hi Abhishek.

I assume you want the try…catch block within the finally to catch the RuntimeException thrown by method2(). This won’t work because the RuntimeException is thrown outside of that try..catch block. In other words, exceptions thrown from within a try…finally block are NOT re-thrown from within the finally block, and thus cannot be caught there.

The solution is to add a catch to the try…finally:
private void method1() {
try {
method2();
} catch (Exception e) {
System.out.println(“Will catch exception from method2.”);
} finally {
System.out.println(“Finally executes”);
}
}

private void method2() {
throw new RuntimeException(“Exception thrown from here.”);
}

By: Abhishek Shrma

Abhishek Shrma — Sat, 30 Jul 2011 06:34:14 +0000

Hi,
I am just doing one interesting thing… Instead of catching a exception properly .. I just put one more try/catch inside the finally clause and expecting that exception will catched be here and no abnormal termination will occur but that doesn’t happen.
Code :

private void method1() {
try {
method2();
} finally {
System.out.println(“Finally executes”);
try {

} catch (Exception e) {
System.out.println(“caught here in finally”);
}
}
}

private void method2() {
throw new RuntimeException(“Exception thrown from here.”);
}
Can you please see over this??

By: Basil Vandegriend

Basil Vandegriend — Fri, 13 May 2011 04:14:07 +0000

@chaumant, it sounds like in your catch blocks you do not want to re-throw an exception – just send an email. In this case execution will continue after the catch blocks, so you could just eliminate the finally block and have the cleanup code afterwards.

By: chaumant

chaumant — Thu, 12 May 2011 06:29:32 +0000

No doubt, Its a good and helpful article.
But it leaves certain questions to me.
I am in the process of developing a code, which actually process set of teams. I wanted to continue if exception is thrown while processing Teams.
And the moment it throws exception, it the process should send a mail for that team.
for(team : Teams){
try{
//process Teams
}
catch(SomeException se){
//Send mail if exception comes
}
catch(Exception e){
//Send mail if exception comes
}
finally{
//cleanup code for the team
continue; // Ofcourse this line is giving waring – “Finally block does not complete normally” and i am also not interested in any warning
}
}

Please advise..what could be alternatives.

By: Basil Vandegriend

Basil Vandegriend — Sun, 17 Apr 2011 20:57:31 +0000

@Student, you can do that by returning a special error code from a catch block. This clearly signals what is going on. Just don’t put a return statement in the finally block.

By: Student

Student — Thu, 14 Apr 2011 22:21:17 +0000

So what is your recommended implementation if the caller of performBusinessOperation() expects a valid return value that only performBusinessOperation() can return. For example, an error code.

By: Arao

Arao — Thu, 08 Apr 2010 20:35:46 +0000

do not u guys read Practical Java??

By: Geza

Geza — Tue, 23 Mar 2010 12:10:28 +0000

Hmmm. The problem in my case was that I used return in the finally block, after I removed that outside, the RuntimeException is propagated appropriately.

Conslusion: do not use return statement in finally block, it can ruin your exception propagation or return policy.