alternatives or complements to layers

Peter Levart peter.levart at
Wed Jan 7 14:39:29 UTC 2015

On 01/07/2015 03:08 PM, Vitaly Davidovich wrote:
> If you're authoring a generic class and call one of these overloaded
> methods, which one is called? What's the return value (for non void ones)?

What's the return value of a lambda expression with multiple returns? 
What's the return value of "condition ? expression1 : expression2" ?

> The final target method is only known when a user instantiates your class
> and provides the type, but not at authorship.

At authorship you know which method will be chosen for each possible 
instantiation. There are only a limited number of methods. There has to 
be a "last-resort" method taking Object parameter(s) or such invocation 
does not compile.

Take for example the overloaded methods of System.out.println(). Which 
method is choosen in this example:

<T> void test(T x) {
}'s always the println(Object) right?

With primitive (and value type) instantiations, there are not so many 
other options. Primitives have more options since they can do implicit 
widening conversions AND boxing, but other value types will either 
choose the method taking exact value type if available, the next 
preference would be the boxed equivalent and finally the fallback to Object.

Regards, Peter

> Sent from my phone
> On Jan 7, 2015 9:04 AM, "Simon Ochsenreither" <simon at>
> wrote:
>>> The other option is to fail compilation if any-T context is calling a non
>>> any-fied method and require user to do a cast on their T to select the
>>> proper overload (including possibly casting to Object).  I don't know if
>> we
>>> want the method "late bound" like that.  Also, suppose the different
>>> overloads return different types - the writer of code has to know what
>> the
>>> type will be upfront.
>> I think the interesting question is "is there a reason why an any-fied
>> parameter couldn't act as a compatible replacement for methods with
>> Object + primitive overloads?". Because that's what any does under the
>> hood already: Create additional methods for non-reference types.

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