Question

Recently I came across a code snippet in a book which sets a Boolean value to a field like this

the input identifier is a List of Strings

if (identifier.size() >= 2) {
    int c = Integer.parseInt(identifier.get(1));
    bulk = (c & 4) == 4;
    hazardous = (c & 2) == 2;
    toxic = (c & 1) == 1;
}

what is the need for unary & operators here?Can’t this be done using a simple
c==4 etc instead of (c & 4)== 4 ?

Answer 1

No, this is a bitwise operation.

Imagine c=7. In that case all conditions would be true.

c = 7;
bulk = (c & 4) == 4; // true
hazardous = (c & 2) == 2; //true
toxic = (c & 1) == 1; //true

In binary, you’d have this:

c = 0111; //4-bit to simplify output
bulk = (c & 0100) == 0100; //
hazardous = (c & 0010) == 0010; //true
toxic = (c & 0001) == 0001; //true

Due to bitwise AND (&) you get 0111 & 0010 = 0010 etc.