Question

I need to represent a value of 0xFF00 as two bytes (in Java). I am trying to do it like this:

int val = 0xFF00;
bytearray[0] = (byte)((val >> 8) & 0xFF);
bytearray[1] = (byte)((val >> 0) & 0xFF);

I know that byte in Java can hold values 0-255. So I expect the first array element to have a value of 255 and the second element to be zero. But what I am getting instead is -1 and 0. What I am doing wrong? What this -1 value mean?

Answer 1

Byte in java is from -128 to 127, not from 0 to 255

-1 is 1111 1111 in two’s complement binary, equal to 255 in unsigned byte.

You aren’t doing anything wrong, you just need to know that if you see -1, it means the byte is representing the bits 1111 1111.