int to byte

[ravian]

I found something strange. Please review the code below:

final int i = 100;
byte b = i;
System.out.println(b);

Output:

100

Removing the final keywords, causes exception.

int i = 100;
byte b = i;
System.out.println(b);

Output:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
	Type mismatch: cannot convert from int to byte

What is the reason? What role final keywords plays here?

Thanks.

[afsina]

This is because once you marked a variable as final, it is now immutable, cannot be changed after the declaration. compiler is intelligent enough to make the decision by allowing it to be set to a byte variable if the value is in range.
the other case, compiler cannot guarantee if there will not be a change on the int before it is assigned to the byte so it does not allow the setting it. Otherwise this code would create a runtime error:

int i = 100;
... lots of code here and i may be altered and set to 10000...
byte b=i; <-- error!!