Java casting / classloader issues

Question

Here is the simplified version of the problem:

 SomeClass c = (SomeClass) obj.getSomeClassParent()

not always but it happens sometimes to t

Answer 1

From the image I see that it looks like a web application. I read 'catalina'. So there is a big chance, that it is a pure classloading problem.

It could happen, for example, if the ImageReader you get from the ImageIO class was loaded by a different classloader (maybe because it's deployed in a different webapp), so the DicomImageReadParam object returned by the getDefaultReadParam() method is an instance of a - technically spoken - different class.