JD.BITMASK happens when int or a long variable is used with bit operation & or | and is then compared to a constant, while the result of the evaluation is known in advance. For example ((a & 0x0f) == 0xf0) is always false because bitmasks are incompatible.

Vulnerability and risk

It is unlikely that the code was intentional, so the error can cause unexpected behavior.

Mitigation and prevention

Fix the bit operator (if it was the cause), or fix the bitmask.

Example 1

10     final static int FLAG = 0x01;
11     static boolean checkMask(int a) {
12         // mistyped, should be &
13         if ((a | FLAG) == 0) return true;
14         return false;
15     }

JD.BITMASK is reported for line 13: Incompatible bitmasks 'a | FLAG' and '0' cause the expression to always be 'false'.

Related checkers