Why is assigning 'int constant -> byte variable' valid, but 'long constant -> int variable' is not?

Question

I have this code snippet:

int i = 5l; // not valid (compile error)
byte b = 5; // valid

What do you think about it?

Why?

Answer 1

This is defined in the JLS #5.2 (Assignment conversion):

If the expression is a constant expression (§15.28) of type byte, short, char, or int, a narrowing primitive conversion may be used if the type of the variable is byte, short, or char, and the value of the constant expression is representable in the type of the variable.

so:

byte b = 5; //ok: b is a byte and 5 is an int between -128 and 127
byte b = 1000; //not ok: 1000 is an int but is not representable as a byte (> 127)
byte b = 5L; //not ok: 5L is a long (and not a byte, short, char or int)
int i = 5L; //not ok: i is not a byte, short or char
int i = 5; byte b = i; //not ok: i is not a constant
final int i = 5; byte b = i; //ok: i is a constant and b is a byte