Final Byte variable

[Prakash Rai]

class Test{
public static void main(String arg[]){
int x=10;
int y=20;
int z=x+y;
System.out.println(z);

byte b1=10+20;   
System.out.println(b1);

byte b2=10;
byte b3=20;
//byte b4=b2+b3;              //It is giving error

 final byte b5=10;                
  final byte b6=20;
byte b7=b5+b6;                   // Why it is not giving error
System.out.println("b7"+b7);

//int x1=10+20l;
long l1=10+20l;

//int x2=10+20.0f;
float f1=10+20.0f;
System.out.println(f1);

//long l2=10.0f+20l;
float f2=10.0f+20l;

byte bb1=10;

//byte bb2=bb1+20.0;
double d1=bb1+20.0;

}
}

Q1. What is diffrence between final byte and bye variable ?

[Vinoth Kumar Kannan]

In the first case, when adding two byte variables, internally they are being promoted to int and so the result is an int, which you must cast back to a byte - because in Java for an arithmetic operation to be performed, the operands must be atleast an int.
In the second case, since you are adding two final byte variables, Java compiler knows that you cannot change them in future and so it performs addition at the compile time itself and assigns it to b7. Here the promoting to int & casting to byte - all are done internally at the compiling stage itself.