Strange behaviour of final keyword..Watch out

Check out this example from "sandeep mock exam"
class MyClass
{
public static void main(String []args)
{
final int i = 100;
byte b = i;
System.out.println("i ="+b);
}
}
ans : o/p i =100
BUT
class MyClass
{
public static void main(String []args)
{
int i = 100;
byte b = i;......(1)
System.out.println(b);
}
}
I get a compiler error as Incompatible type declaration, so when I cast line (1) as byte b = (byte)i; it works fine with o/p 100
why is this strange behaviour with " final keyword"?, I am confused.
can somebody clear my doubt?
Thanks in advance
satheesh

plz check Rhalid book.

This looks really tricky. Can someone explain more?

I reallly could not understand what is given in the book when I read it, could u pls explain to me in brief
Thanks in advance

Hi, I think it has to do with compiling rules. When an int is declared final, its value is set forever at compile time. The compiler knows for sure that 100 is within the range of byte value. On the other hand, without declaring an int final, the compiler will have no way of knowing for certain that the int's value will be within byte's range. Therefore, without the final keyword, compiler requires the int to be cast to byte.

I must've seen this example at least three times in the last month. It's funny how some things just keep popping up.

Thanks bob for ur detail explanation
now I got it..,
satheesh

Originally posted by Tom Tang:
This looks really tricky. Can someone explain more?

hi Tom,
Tom java compiler goes for optimization and replaces the final variables with the values present in that.
Note that the final method call is faster than a non-final method call bcoz in case of final method it doesnt have to go for dynamic data lookup which is slow .
Cherry

Hey...Satheesh Kumar,
Can u tell me where i can find this particuler Mock Exam??
************T H A N K S IN A D V A N C E ***************
round6

I think this is the one
http://www.tipsmart.com/javacert/ptp/basics.htm
Varsha

thanks Varsha