exception handling

[Naresh Chaurasia]

hi, i have following code

 
class sample
{
public static void main(String str[])
{
try
{
int i = 1/0;
}
catch(CDCRuntimeExceptionHandler e)
{
System.out.println("you are here");
System.out.println(e.getMessage());
}
}
 

}
 

class CDCRuntimeExceptionHandler extends RuntimeException{
 
public CDCRuntimeExceptionHandler() {
super();
}
 
public CDCRuntimeExceptionHandler(String errMsg) {
super(errMsg);
}
}
 

why is CDCRuntimeExceptionHandler not able to catch ArithmeticException and display you are here

[Keith Lynn]

Because ArithmeticException is not a subclass of CDCRuntimeExceptionHandler

[Pinkal Patel]

CDCRuntimeExceptionHandler not able to catch ArithmeticException

Cous...

Class B extens A {}
Class C extans A {}

Can you use..
B=C

[Naresh Chaurasia]

But the CDCRuntimeExceptionHandler is super class of ArithmeticException and if i am not wrong the super class can catch sub-class exception.

[Keith Lynn]

Originally posted by N Chaurasia:
But the CDCRuntimeExceptionHandler is super class of ArithmeticException and if i am not wrong the super class can catch sub-class exception.

How is CDCRuntimeExceptionHandler a superclass of ArithmeticException?
[ June 19, 2006: Message edited by: Keith Lynn ]

[Naresh Chaurasia]

pinkal,
i cannot say B=C, but i can say : CDCRuntimeExceptionHandler = ArithmeticException and CDCRuntimeExceptionHandler = RuntimeException since in both cases the CDCRuntimeExceptionHandler is super class.

[Naresh Chaurasia]

keith when i say CDCRuntimeExceptionHandler is super class of ArithmeticException , i mean that CDCRuntimeExceptionHandler is extending RuntimeException and RuntimeException is allowed to catch ArithmeticException

 
class sample
{
public static void main(String str[])
{
try
{
int i = 1/0;
}
catch(RuntimeException e)
{
System.out.println("you are here");
System.out.println(e.getMessage());
}
}
 

}
 

[Keith Lynn]

But that doesn't make CDCRuntimeExceptionHandler a superclass of ArithmeticException.

[Naresh Chaurasia]

yes true, but CDCRuntimeExceptionHandler is extending RuntimeException and then CDCRuntimeExceptionHandler should inherit the feature of RuntimeException and hence be allowed to catch the ArithmeticException....i agree that CDCRuntimeExceptionHandler is not super class of ArithmeticException

[Keith Lynn]

No, it doesn't inherit that property.

CDCRuntimeExceptionHandler is a subclass of RuntimeException.

But it doesn't have any relation to ArithmeticException.

You'll need to make the parameter in the catch block ArithmeticException or one of its superclasses.

[Naresh Chaurasia]

You'll need to make the parameter in the catch block ArithmeticException or one of its superclasses

RuntimeException is super class of ArithmeticException

[Keith Lynn]

But CDCRuntimeExceptionHandler isn't.

[Naresh Chaurasia]

ok, i think i got your point.....but in that case, if i am writing my custom exception handler for my application, then how will i catch all the exception and handle them...

lets consider the original code is posted.. if there is some run time exception occuring that what can i do to handle that exception.

 
try
{
int i = 1/0;
}
catch(Exception e)
{
throw new CDCRuntimeExceptionHandler(e.getMessage());
}
 

if i do something like this, is it fine

[Naresh Chaurasia]

my basic purpose of throwing is CDCRuntimeExceptionHandler is that i have defined error file corresponding to CDCRuntimeExceptionHandler in my web.xml so that when ever my application throws error i can handle it declaratively using web.xml

<error-page>
<exception-type>com.util.CDCRuntimeExceptionHandler</exception-type>
<location>/login/LoginExceptionScreen.jsp</location>
</error-page>
 

[Keith Lynn]

Well you can. But it may not do what you want.

If you make the net too wide, then it will catch all exceptions.

You might want to rethink how you're handling exceptions.

[Naresh Chaurasia]

i agree, but if i define custom exception than i face the problem...can u suggest me some way to work with custom exceptions...so that i can log error message specific to my application

[Keith Lynn]

If you're going to open the net wide, then you could use the instanceof operator or getClass() to determine the type of exception.

[Naresh Chaurasia]

ok if i do not want to open the net wide, what is other way i can use to achieve custom exception handling...

[Keith Lynn]

You can have several catch blocks.

[Pinkal Patel]

Hi Chaurasia,

i can say : CDCRuntimeExceptionHandler = ArithmeticException and CDCRuntimeExceptionHandler = RuntimeException since in both cases the CDCRuntimeExceptionHandler is super class.

CDCRuntimeExceptionHandler = ArithmeticException // Not Alloved Pls Check
CDCRuntimeExceptionHandler = RuntimeException // This is valid
CDCRuntimeExceptionHandler is super class // I thing this is not currect

RuntimeException is super calss of both the Exception CDCRuntimeExceptionHandler and ArithmeticException

So if we catch the RuntimeException both will catch in runtime excpetion.

[Naresh Chaurasia]

thnx Pinkal,
i have found out where i was going wrong...have you worked on custom exception handling.....handling different kinds of exception in your application, catching them and logging them, by defining custom exception handler

[Naresh Chaurasia]

thnx Pinkal,
i have found out where i was going wrong...have you worked on custom exception handling.....handling different kinds of exception in your application, catching them and logging them, by defining custom exception handler...can you give me some suggestion about it

[Pinkal Patel]

Sure,

But it will depande on the your requerment and application architechture.

[Finner Jones]

Hi guys,

I would suggest the following:

 
public class TestCDCRuntimeException {
 
public static void main(String[] args) {
try {
[B]doSomeArithmetic();[/B]
} catch (CDCRuntimeExceptionHandler rte ) {
System.out.println("you are here");
} 
}

    [B]private static void doSomeArithmetic() throws
                                      CDCRuntimeExceptionHandler {
try {
int i = 1/0;
} catch (ArithmeticException ae) {
throw new CDCRuntimeExceptionHandler();
}
}
     [/B]
}
 

class CDCRuntimeExceptionHandler extends RuntimeException {
public CDCRuntimeExceptionHandler() {
}

public CDCRuntimeExceptionHandler(String errMsg) {
System.out.println(errMsg);
}
}
 

By creating and throwing your custom exception in an method you can then catch the custom exception when you call the method.

Not sure if this helps.

Finner

[Pinkal Patel]

As I told,

It is totaly depand on the Application requrment.

This is perfecly Legal for this program but not help full in real application.