Re: use of assert in Java [vs. exceptions]
Giovanni Azua wrote:
I think it depends, if that supposed method would be "exposed" e.g. a method
exposed as Web Service then the input validation rule applies, it would then
be "good defensive programming". If, on the other hand, the supposed method
belongs to an Utils/Support API e.g. Math then I would use assertions rather
than defensive checks.
Assertions are not a replacement or substitute for "defensive" checks, but
complementary to them.
It is unlikely that someone develops a professional UI that would let users
enter values that are passed directly to Utils/Supports API or primitive
operator calls e.g. "a / b" that would be a very bad design. In this case as
I mentioned before you would have a presentation layer (input conditional
checking) or enforced by the UI widgets e.g. combo boxes rather than input
fields, then the defensive filter layer [1] and finally the call to the
assert-based f(a,b) = "a / b".
I think we agree on this. You are making essentially the same point I've been
making.
I do think that you're glossing over the fact that the division operator also
adheres to what I have been suggesting - it throws 'ArithmeticException' when
you attempt integral division by zero, and returns a valid value when you
attempt floating-point division by zero. So even if you let the input value
from the presentation layer directly through to the division, division by zero
gets handled. This is consistent with my recommendation and that of others,
that all inputs should be handled.
I would be curious to know what your handler would look like for an
'ArithmeticException', maybe I will learn something new today, and I mean it
without any bad intentions. I think any piece of code leading to an
'ArithmeticException' will need to be reviewed, fixed and better unit
tested.
Again I agree with you. As for my handler, it would depend on the desired
product behavior. It might look like this:
public int sumDivByInput( int divisor )
{
if ( divisor == 0 )
{
return 0;
}
assert divisor != 0;
int sum = 0;
for ( int divid : dividends )
{
sum += divid / divisor;
}
return sum;
}
--
Lew