widening conversion

[akash azal]

class Casting {
public static void main(String [] args) {
long l = 130L;
byte b = (byte)l;
System.out.println("The byte is " + b);
}
}

can anyone tell while narrowing conversion how the result is calculated

[Henry Wong]

long l = 130L; 
byte b = (byte)l; 

Quite simply, Java just chops off the unwanted bytes for the cast.... Here is the long in binary....

l = 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 1000 0010

Here is the byte in binary....

b = 1000 0010

Now, if you notice that the high bit of this byte is a one. This means that it is a negative number. To get full details on how negative numbers are represented, just google "twos complement".

And after you read how twos complement works....

b = 1000 0010

~b = 0111 1101

~b + 1 = 0111 1110 = -b = 126

b = -126

(hope I got the math right ... )

Henry

[Senthil Kumaran]

you no need to worry about the exact conversions happening in the compiler inside,.
but for the basic knowledge of literals conversions you need study them, then its easy to understand about wrapping conversions.,