If you don’t know the type at compile time, then you can’t unbox because you have nowhere to put it – all you can do is store it in an object, which is: boxed. The same also applies to reference-types like string: you can’t cast it to the right type if you don’t know the … Read more
Both Integer and Long are subclasses of Number, so I suspect you can use: long ipInt = ((Number) obj.get(“ipInt”)).longValue(); That should work whether the value returned by obj.get(“ipInt”) is an Integer reference or a Long reference. It has the downside that it will also silently continue if ipInt has been specified as a floating point … Read more
what is so hard technically to include primitive types when talking about Generics ? In Java’s case, it’s because of the way generics work. In Java, generics are a compile-time trick, that prevents you from putting an Image object into an ArrayList<String>. However, Java’s generics are implemented with type erasure: the generic type information is … Read more
Yes, special treatment. The JIT compiler is keenly aware of the way boxed value types work. Which is in general what makes value types acting a bit schizoid. Boxing involves creating a System.Object value that behaves exactly the same way as a value of a reference type. At that point, value type values no longer … Read more
The issue is that Integer.valueOf returns an Integer, not an int, but your someOtherMethod expects an int. Findbugs is basically warning you that you’re doing it a long-winded way that involves potentially creating an object (the Integer) that you don’t need which you’re then immediately going to unbox by passing it to someOtherMethod(int), e.g.: String … Read more
I don’t know why vectors of pairs are stored as pairs of vectors, but you can easily write instances for your datatype to store the elements sequentially. {-# LANGUAGE TypeFamilies, MultiParamTypeClasses #-} import qualified Data.Vector.Generic as G import qualified Data.Vector.Generic.Mutable as M import Control.Monad (liftM, zipWithM_) import Data.Vector.Unboxed.Base data Point3D = Point3D {-# UNPACK #-} … Read more
If you need different behaviour when you’re dealing with a value-type then you’re obviously going to need to perform some kind of test. You don’t need an explicit check for boxed value-types, since all value-types will be boxed** due to the parameter being typed as object. This code should meet your stated criteria: If value … Read more
I believe this was a bug which seems to have been fixed. Throwing a NullPointerException seems to be the correct behavior, according to the JLS. I think that what is going on here is that for some reason in version 8, the compiler considered the bounds of the type variable mentioned by the method’s return … Read more
You can only unbox a value type to its original type (and the nullable version of that type). By the way, this is valid (just a shorthand for your two line version): object i = 4; decimal d = (decimal)(int)i; // works even w/o decimal as it’s a widening conversion For the reason behind this … Read more
When it comes to collections, generics make it possible to avoid boxing/unboxing by utilizing actual T[] arrays internally. List<T> for example uses a T[] array to store its contents. The array, of course, is a reference type and is therefore (in the current version of the CLR, yada yada) stored on the heap. But since … Read more