Compile time constants

Question

Hey i have a doubt regd compile time constants
byte a =10,b=20;
byte c= a+b; // compile time error coz a+b may exceed byte limit
int a=10,b=20;
int d=a+b; // not showing any error . a+b may exceed int limit
can anyone clear me int his

Answer 1

public class Test {
    public static void main(String[] args) {
        byte a = 10, b = 20;
        byte c = a+b;  //syntax error: "possible loss of precision"
        final byte d = 10, e = 20;
        byte f = d+e;  //OK
}It's not about overflow, but implicit casting: in the expression a+b, bytes a and b
are widened to int and the addition is 32-bit addition -- the result is an int.
When you attempt to assign an int to a byte, the top three bytes are discarded,
hence the syntax error "possible loss of precision". You get the same
error message when assigning a double to a float.
Why don't I get the syntax error with my d-e-f example? Variables d and e
are declared final, so the compiler folds in their values. Thus it know 10+20
is 30 and that the int value 30 fits into one byte.