The Java Language Specification (JLS), §15.17.3, "Remainder Operator %" [JLS 2011], states,
The remainder operation for operands that are integers after binary numeric promotion (§5.6.2) produces a result value such that
(a/b)*b+(a%b)
is equal toa
. This identity holds even in the special case that the dividend is the negative integer of largest possible magnitude for its type and the divisor is-1
(the remainder is0
). It follows from this rule that the result of the remainder operation can be negative only if the dividend is negative, and can be positive only if the dividend is positive; moreover, the magnitude of the result is always less than the magnitude of the divisor.
...
Incorrectly assuming a positive remainder from a remainder operation can result in erroneous code.
Bibliography
...