Java compile time error in case of casting

Question

The below code gives me compile time error Type mismatch: cannot convert from int to byte

int i = 10;
byte b = i;

but the below doesn't

 final int i = 10;
 byte b = i;

I don't understand why compiler is behaving in case of final?

Answer 1

I think it's because 10 fits in a byte, but if the integer was something that takes more than 8 bits then it wouldn't be able to properly do this assignment anymore.

Edit

To clarify, making it final is allowing the compiler to treat the int as a constant so it can do constant folding. It's probably preventing the assignment with the non-final int because it doesn't know that value at compile time and it could be way bigger than what a byte can hold.

Answer 2

Case 1: compile error because an int might not fit into a byte; an explicit cast is necessary
Case 2: the compiler compiles the 2nd statement to byte b = 10; (as i is final), so no error