Question

I’m curious to know why, when I compare a byte array with a value…

boolean match = ((data[0] & 0xFF) == 0xFE);

…returns true, while…

boolean match = (data[0] == 0xFE);

…does not? data is a byte array with

data[0] = (byte) 0xFE;

Answer 1

boolean match = ((data[0] & 0xFF) == 0xFE);

compares integers as 0xFF is an integer, this expression will scale up your byte data[0] to an int and compare what’s inside the parenthesis to a second int 0xFE(254). As you say data[0] is (byte)0xFE, it will first be scaled to the integer 0xFE and compared to the integer 0xFE, so this works.

boolean match = (data[0] == 0xFE);

compares a byte to the int 0xFE : 254

data[0] = (byte) 0xFE; 

is a byte (so it’s signed) and its value is -2.

-2 is not equal to 254, so that’s why you must compare data[0] as a byte or as scale it up to an integer before comparing it the integer 0xFE.

A simpler comparison could be

boolean match = (data[0] == (byte)0xFE);