Automatic typecasting during overlapping assignment (+=, *=, ...) :
sum += Math.pow();

Explicit type casting:
sum = sum + (int) Math.pow();

this is strange. When I write this code:

int sum = Math.pow(1,2);

I will get an error message which says: "Cannot convert from double to int".

But why does your notation ->> sum += Math.pow(); works?

if you rewrite this to -> sum = sum + Math.pow(); <<- it wont work!

Could you please explain?