++i + ++i + ++i in Java vs C

Question

int i=2;
i = ++i + ++i + ++i;

Which is more correct? Java's result of 12 or C = 13. Or if not a matter of correctness, please elaborate.

Answer 1

Java guarantees (§15.7.1) that it will be evaluated left-to-right, giving 12. Specifically, ++ has higher precedence that +. So it first binds those, then it associates the addition operations left to right

i = (((++i) + (++i)) + (++i));

§15.7.1 says the left operand is evaluated first, and §15.7.2 says both operands are evaluated before the operation. So it evaluates like:

i = (((++i) + (++i)) + (++i));
i = ((3 + (++i)) + (++i)); // i = 3;
i = ((3 + 4) + (++i)); // i = 4;
i = (7 + (++i)); // i = 4;
i = (7 + 5); // i = 5;
i = 12;

In C, it is undefined behavior to modify a variable twice without a sequence point in between.