exception - how to handle in real projects ...

[ankur rathi]

Hi ,
I am confuse with this two approach :

 
one
---
 
void my() throws MyException{
 
try {
 
    // some code that may throw different types of exception   
 
} catch (ClassNotFoundException cnfe) {
    throw new MyException("Class not found :",cnfe);
} catch (InstantiationException ie) {
     throw new MyException("Class can not instatiated :",ie);
} catch (IllegalAccessException ile) {
     ile.printStackTrace();
     throw new MyException("Illegal Access :",ile);
}
 
}
 

two
---
 
void my() throws MyException {
     try {
 
          // some code that may throw different types of exception   
 
     } catch(Exception e) {
           throw new MyException("Some exceptions occur "+e);
     }
}
 
where MyException is custom exception .
 

please explain me , which one is good for real projects , both point of view ( line of code , efficient ) ...

Thanks a lot .

[Ilja Preuss]

This has virtually no impact on performance. Therefore moving to Java in General (intermediate)...

[Ashish Chopra]

In a real project you might need different handling for different exceptions, for e.g: you'll need different handling for a NullPointerException when compared to the handling of a FileFormatException. Hence, the need for different try-catch blocks for both.

Even otherwise, it is always better to have specific exception handling before writing "catch(Exceptioon e)" that handles a generic exception, for those exceptions that you are expecting your code to generate. For other unpredictable exceptions, the generic try-catch block is good enough.

Coding exception-specific catch blocks might take some coding effort but is Good coding. This also helps when you are writing unit test cases. I do not think there is much performance overhead, as anyway only one of them would be executed.

[Stan James]

In my experience I've almost never handled two exception types differently. Generally any failure in a routine means the user is not going to get something they want, so I can catch Exception and give them the bad news. If you're really going to code different responses, you have to check the different exception types.

You also have to decide whether to throw different types just in case somebody who calls you wants to take different actions. If you always throw Exception callers may wind up trying to parse the message to decide what to do, and that's a Bad Thing.

Hope that's useful!