Java – Why doesn’t Java autoboxing extend to method invocations of methods of the autoboxed types

autoboxingjava

I want to convert a primitive to a string, and I tried:

myInt.toString();

This fails with the error:

int cannot be dereferenced

Now, I get that primitives are not reference types (ie, not an Object) and so cannot have methods. However, Java 5 introduced autoboxing and unboxing (a la C#… which I never liked in C#, but that's beside the point). So with autoboxing, I would expect the above to convert myInt to an Integer and then call toString() on that.

Furthermore, I believe C# allows such a call, unless I remember incorrectly. Is this just an unfortunate shortcoming of Java's autoboxing/unboxing specification, or is there a good reason for this?

Best Solution

Java autoboxing/unboxing doesn't go to the extent to allow you to dereference a primitive, so your compiler prevents it. Your compiler still knows myInt as a primitive. There's a paper about this issue at jcp.org.

Autoboxing is mainly useful during assignment or parameter passing -- allowing you to pass a primitive as an object (or vice versa), or assign a primitive to an object (or vice versa).

So unfortunately, you would have to do it like this: (kudos Patrick, I switched to your way)

Integer.toString(myInt);