Why is this an issue?
When the modulus of a negative number is calculated, the result will either be negative or zero. Thus, comparing the modulus of a variable for
equality with a positive number (or a negative one) could result in unexpected results.
Noncompliant code example
public boolean isOdd(int x) {
return x % 2 == 1; // Noncompliant; if x is an odd negative, x % 2 == -1
}
Compliant solution
public boolean isOdd(int x) {
return x % 2 != 0;
}
Resources
- CERT, NUM51-J. - Do not assume that the remainder operator always returns a
nonnegative result for integral operands
- CERT, INT10-C - Do not assume a positive remainder when using the % operator
