Why JPA entity class and its methods must not be declared final?

Because persistence providers make proxies of objects using some library like CGLIB or javassist. These proxies are creating runtime subclasses of the entities. That's why they should not be final.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.