Variable exception target

[D Rog]

Class use = null;
try {
use = Class.forName("javax.jnlp.UnavailableServiceException");
} catch(ClassNotFoundException cne) {}
catch(Error e) {}
if (use != null)
try { 
   ps = (PersistenceService)ServiceManager.lookup("javax.jnlp.PersistenceService"); 
} catch (use e) {  // can't find symbol
   ps = null; 
}

Why? Why Java restrics me using class literal instead of class variable? I want to have code working when jnlp package available and when not. Do not tell me about work around as catch Throwable and then figure if it's UnavailableServiceException. Any elegant solution of switchable using API?

[avaya sahu]

Hi,
It seems that you are trying to play with java language feature. When catch statement is used compiler should be informed about the type of the exception so that it can check whetehr the order of catch are correct and whether it is inherited form the proper class(e.g Excpetion,RuntimeException, Throwable) by allowing class literal it will have no clue of the class type an its heirachy.

I don'tnow any elegant soln to the problem. but you can catch throwable then use reflection to check whether the exception is of expected type.
...
cath(Throwable th)
{
if (th.isAssingable(use))
{
......................
}
}

[Stefan Wagner]

Class use = null;
//...
use = Class.forName ("javax.jnlp.UnavailableServiceException");
//...
if (use != null)
//...
catch (use e) // can't find symbol

You're using the name of an Object, where a Type is expected.
That's equivalent for writing:

 
public isSeven (7 a) 
{
        return (7 == a);
}
// or 
int b;
public isSeven (b a) 
// instead of 
public isSeven (int a) 

The compiler doesn't even look at your 'use', but claims "can't find symbol", because it is looking for that symbol only in the list of types.
[ May 23, 2005: Message edited by: Stefan Wagner ]

[D Rog]

Thanks, I understand you. However your illustration a bit lacking. Look in avaya sahu's sugestion.
Define your parameters as Objects and then figure out an actual class.