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List Interface

Akhil Maharaj
Ranch Hand

Joined: Sep 29, 2007
Posts: 63
can any body give good explantion why in the following code Line 2 is giving me an exception ? I can do the same thing with Line 1 . No problem with Line 1 at all .

[ October 10, 2007: Message edited by: Burkhard Hassel ]
Mixirica Roxa

Joined: Sep 25, 2007
Posts: 3
The problem is fault the cast

change is line

per this
Burkhard Hassel
Ranch Hand

Joined: Aug 25, 2006
Posts: 1274
Howdy Akhil,

welcome to the Ranch!

Tricky problem.

On line 1 Object j = l.get(x); // Line 1
the "get" should return an object of type String, you can nicely assign this to a variable of type Object.
At runtime, the object returned is not a String but the Integer-object 123.
This can also be assigned to an Object without problems.

In line 2 however
at runtime you will also get the same 123 Integer object back, and again a String is expected.
But this time the Integer-object is not assigned to an Object variable but to a String variable. This must happen somewhere in the getClass-method. And then the cast fails and you have the exception.
I don't know what happens exactly in the getClass() - method. It is native.

By the way, the getName() should not be the problem, the exception comes also when you delete that part.


all events occur in real time
Burkhard Hassel
Ranch Hand

Joined: Aug 25, 2006
Posts: 1274
Howdy "Vitor Hugo" !

Thanks for one of your first contributions to this forum and...

Welcome to the Ranch!

Hope you'll enjoy.

Only one small issue: The Java Ranch follows a certain policy regarding user names.
The main reasons why and a link how to change yours you'll find here:

So, could you please change your user name before your next posting?
It will not affect anything you've already posted here. Just your user name will update.

I'm posting this because I am one of the moderators of this forum.

I agree. Here's the link:
subject: List Interface
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