Why does Math.round return a long but Math.floor return a double?

Question

Why the inconsistency?

Answer 1

floor would have been chosen to match the standard c routine in math.h (rint, mentioned in another answer, is also present in that library, and returns a double, as in java).

but round was not a standard function in c at that time (it's not mentioned in C89 - c identifiers and standards; c99 does define round and it returns a double, as you would expect). it's normal for language designers to "borrow" ideas, so maybe it comes from some other language? fortran 77 doesn't have a function of that name and i am not sure what else would have been used back then as a reference. perhaps vb - that does have Round but, unfortunately for this theory, it returns a double (php too). interestingly, perl deliberately avoids defining round.

[update: hmmm. looks like smalltalk returns integers. i don't know enough about smalltalk to know if that is correct and/or general, and the method is called rounded, but it might be the source. smalltalk did influence java in some ways (although more conceptually than in details).]

if it's not smalltalk, then we're left with the hypothesis that someone simply chose poorly (given the implicit conversions possible in java it seems to me that returning a double would have been more useful, since then it can be used both while converting types and when doing floating point calculations).

in other words: functions common to java and c tend to be consistent with the c library standard at the time; the rest seem to be arbitrary, but this particular wrinkle may have come from smalltalk.