Is this really widening vs autoboxing?

Question

I saw this in an answer to another question, in reference to shortcomings of the Java spec:

There are more shortcomings and this is a subtle topic. Check

Answer 1

Another interesting thing with this example is the method overloading. The combination of type widening and method overloading only working because the compiler has to make a decision of which method to choose. Consider the following example:

public static void hello(Collection x){
   System.out.println("Collection");
}

public static void hello(List x){
   System.out.println("List");
}

public static void main(String[] args){
   Collection col = new ArrayList();
   hello(col);
}

It doesn't use the run-time type which is List, it uses the compile-time type which is Collection and thus prints "Collection".

I encourage your to read Effective Java, which opened my eyes to some corner cases of the JLS.