method call with generic type parameter

[fickle kelp]

I'm working on a simple function that has an instance of a class (in a loop) and calls a method which requires a parameter of the generic type of that class.

unfortunately i can't find any way to get this to compile, even with access to the specific Class object which the generic type is supposed to represent (via leaving a "hint" of the type in the instance)

for(Info<?> i : data.values()) {
    if (i.atDefault())
        i.setValue(base.data.get(i.getName()));
}

the error i get is in setValue:
The method setValue(capture#46-of ?) in the type Info<capture#46-of ?> is not applicable for the arguments (Info<capture#48-of ?>)Java(67108979)

the definition of setValue() is like public void setValue(T newValue). So i understand that the compiler has no way to know that the parameter base.data.get(i.getName()) is of type T. However, even if i use a Class.cast() to the type I expect T to be, the compiler does not accept this even though it should always work.

Casting the parameter to Object doesn't work because setValue() expects T, not Object. Casting to T doesn't work because it doesn't know what that is in the scope. The ? unknown type syntax isn't applicable here. As far as I can tell, there is no way for the compiler to know that any cast that I make is actually of type T, even if it happens to be, or I know that it is.

I'm stumped on how to actually get this to work, all I want is to be able to call a function on any Info object and pass it parameters of the type of which it is.

[bleak juniper]

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[fiery knoll]

Dude, you used <?>

Nothing will be accepted

<?> is not <T>, what would a cast achieve?

[fickle kelp]

is there an alternate way to accomplish what I'm trying to do?

The list data.values() has Info objects with various different generic types

so I can't do for(Info<AnySpecificType> i : data.values())

[fickle kelp]

i can accept that Info<?> may not be the way to go but I don't know how to achieve my end goal, which is to have a list of Info with various types, and call a Info.setValue() function with a parameter of the type that they have

[fiery knoll]

You have contradictory goals

You don't have a type consistency in place, and you're trying to use a system that guarantees type consistency

If you really want to do something like that, then you have to ignore generics on that part

[fickle kelp]

i could abandon generics but I would have to write a lot of duplicated code for every type that i wanted Info to represent

for example i'd have to write a setValue() in a subclass for each of them when it is all the same code over and over

[fiery knoll]

I said ignore generics on that part. Not necessarily remove them entirely

Anyway, you could flat-out remove the <> part altogether so that generics aren't checked, which is your goal as you don't have type safety on that part.

Or you could "lie" and say it's Info<Object> in the loop so that it will accept anything inside the loop. You'll need to tell the compiler to just accept the lie by casting

[fickle kelp]

i think i figured out something that works - i changed setValue() to accept type Object, then check instanceOf using the type hints i have, and throw ClassCastException if it has been used incorrectly.

i'll keep what you said in mind though, because those also seem like they would work

i appreciate the help!