Bit level operations in Java

Question

I'm trying to make some bit operations in Java for applying masks, represent sets etc. Why:

int one=1;
int two=2;
int andop=1&2;
System.out.println(andop);

Prints a "0" when is supposed to be "3":

0...001
0...010
_______
0...011

And how can I get that behavior?

Thanks in advance

Answer 1

Better solution is to use enums with int values ONE(1), TWO(2) etc, and EnumSet.

From JavaDoc:

Enum sets are represented internally as bit vectors. This representation is extremely compact and efficient. The space and time performance of this class should be good enough to allow its use as a high-quality, typesafe alternative to traditional int-based "bit flags."

Answer 2

& must be both 1

0...001
&...&&&
0...010
_______
0...000

answer = 0
| is or ,one 1 is OK

0...001
|...|||
0...010
_______
0...011

answer = 3

Answer 3

You're looking for a bitwise "OR", not "AND":

int both = one | two;

"OR" says: "bit n should be 1 if it's 1 in input x *or* it's 1 in input y"

"AND" says: "bit n should be 1 if it's 1 in input x *and* it's 1 in input y"

Answer 4

You mixed up bitwise OR and bitwise AND

Answer 5

Use the binary 'or' operator:

int andop = 1 | 2;

The binary 'and' operator will leave bits sets that are in both sides; in the case of 1 and 2 that is no bits at all.