final int prime = 31;

Question

Shoudnt the variable prime be capitalised due to the final keyword?

Answer 1

"final" use to declare a constant and you can set name of constant same as variable.
ex: final int PRIME=31;

Answer 2

You're right it's just a convention but not compulsory for someone who didn't care about the standard.

Answer 3

Be cool and Follow dem standards!! 😎