Multiple if statements

[dojob]

I have come across this in a Java book. May i know why are there implementing multiple if statements instead of else if statements.
It seems that using else if is more efficient and also the month is mutually exclusive. so i have no idea if there are implementing multiple if instead of else if or switch.

    public static int getNumberOfDaysInMonth(int year, int month){
        if(month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12)
            return 31;
        if(month == 4 || month == 6 || month == 9 || month == 11)
            return 30;
        if(month == 2) return isLeapYear(year) ? 29: 28;
        
        return 0;
    }

[gimbal2]

Less typing perhaps? Either way works in this particular case because the code returns in each if statement, there is no way that any of the ifs further down the line is reached once one of them resolves to true.

And please, forget about efficiency when you're talking about snippets of code. Focus on code readability.

[sehudson]

In this example, it doesn't matter too much because they are returning the days inside the if statements, and once that happens, none of the other conditions will be evaluated. But you are correct, if/else would work as well.

[DarrylBurke]

... and if you're looking for both efficiency and readability, that really ought to be a switch statement with fall-through.

db

[gimbal2]

... and if you're looking for both efficiency and readability, that really ought to be a switch statement with fall-through.

db

THAT's a personal opinion not shared by everyone.

[sehudson]

THAT's a personal opinion not shared by everyone.

To an extent it is, but I think he is right. Switch statements in general are easier to read, and look cleaner. They provide well defined code boundaries so it can be easier to traverse the logic.

[JosAH]

THAT's a personal opinion not shared by everyone.

I don't know if it's so personal; have a look at those if statements and assume they're executed in a Harvard memory model; what happens is: fetch from RAM (month), fetch from ROM (the numeric literal) and over and over again; if there is a cache this scenario would kill its coherence. It doesn't matter much on a von Neumann memory model (i.e. ordinary PCs) but a switch statement or a lookup table would be better for a Harvard memory model ...

kind regards,

Jos

[gimbal2]

I respect your and Dedicated Beerdrinker's opinion. I just don't share it ;) Because of the fall-through 'programming mistake waiting to happen' aspect of it, should you be curious why I just have to be non-conformant. I also think it is needlessly verbose, but so is a large chain of if-else statements so in any case, I lose.

edit: crud, I lost the quote. That was @sehudson

[JosAH]

I respect your and Dedicated Beerdrinker's opinion. I just don't share it ;) Because of the fall-through 'programming mistake waiting to happen' aspect of it, should you be curious why I just have to be non-conformant. I also think it is needlessly verbose, but so is a large chain of if-else statements so in any case, I lose.

edit: crud, I lost the quote. That was @sehudson

If someone doesn' know how a switch statement works in C/C++/Java/etc, that someone is not supposed to touch any code imho. I personally prefer a (dense) lookup table here; it doesn't hurt different memory models and it's just as concise as a switch statement (and it only takes 13 bytes of storage ;-).

kind regards,

Jos

[dojob]

Thanks for all the reply. I thought that there is particular reason for author of the book using if in this case.