Tell me Why ?

[Sherry Jacob]

Hi All,
I compiled this code...

public class Test
{
static final int i = 100;
public static void main(String args[])
{
byte b = i;
System.out.println(b);
}
}

and this code...

public class Test
{
static int i = 100;
public static void main(String args[])
{
byte b = i;
System.out.println(b);
}
}

The first code compiles but the second does not. Why ?
Please help.

[Barry Gaunt]

Sherry, please give your topic a meaningful title, and please tell us the compilation error you get. Is the error given by the compiler not meaningful?

Yes, I can see why the second does not compile:In the first case i is a compile time constant within the range of a byte (-128 to 127). In the second it is not a constant and the compiler cannot guarantee in all possible cases that at the time of the assignment that i still contains 100.
[ September 06, 2005: Message edited by: Barry Gaunt ]

[amit g]

Hi Sherry,

Reason is simple in the first code u declared variable as a final and final
variables are constants so compiler knows that the value of this particular variable will not change in runtime ie. will not change from 100.
So it will not go out of range.

In other way compiler replaces all final variable with there values at compile time as in ur code


statement
byte b = i; //for first code

will replace to

byte b = 100; before compilation then compilation will occur.


but in second snap shot of code i

byte b = i ;

will not replace to

byte b =100;

it will simply

byte b = i;


Cheers
Amit Goyal

[Thomas Drew]

Sherry, the reason your second file fails to compiles is because i is promoted to an integer before it is assigned to the byte b. To fix the problem you will have to cast i back to a byte (byte) i.

[Barry Gaunt]

because i is promoted to an integer before it is assigned to the byte b

i is already an int, it does not have to be promoted.

[A Kumar]

http://www.coderanch.com/t/250545/java-programmer-SCJP/certification/Final-variable

Check this one out..

Regards