Why do integer div and mod round towards zero?

问题

Unlike in C, in Java is the result of x/y and x%y well-defined even for negative operands. Surprisingly, it's defined by rounding towards zero, and not by rounding down (i.e., towards negative infinity). Does anybody have taken any advantage of this definition?

^{In most cases I just don't care, but sometimes I had to work around this, e.g., when computing an index using modulo array.length.}

^{This is no rant, I'm really interested if there are uses for this definition.}

回答1:

It's easier to implement a division routine if you can round toward zero. Often, a division involving a negative is sign-flipped, and then the division carried out on a positive equivalent, and then the answer flipped back again. So the effect is naturally going to be round toward zero.

回答2:

Here's one example where it's useful, however slightly:

maxPage = (rows.length - 1) / ROWS_PER_PAGE

(No need to special case for maxPage = 0 when rows.length = 0, assuming ROWS_PER_PAGE > 1.)

来源：https://stackoverflow.com/questions/5682625/why-do-integer-div-and-mod-round-towards-zero