Challenge 2: A Generic Factory Using the new() Constraint — Possible Solution
====================================================================

Program.cs:

class Widget
{
    public string Label = "default widget";
}

class Gadget
{
    public int Count = 0;
}

static T CreateDefault<T>() where T : new()
{
    return new T();
}

Widget w = CreateDefault<Widget>();
Gadget g = CreateDefault<Gadget>();

Console.WriteLine(w.Label);
Console.WriteLine(g.Count);

Output:

    default widget
    0

Explanation:
The where T : new() constraint tells the compiler that whatever type
T ends up being, it must have a public parameterless constructor --
this is what makes `new T()` legal at all inside CreateDefault<T>().
Both Widget and Gadget satisfy this constraint (neither declares any
constructor, so each gets an implicit public parameterless one), so
CreateDefault<Widget>() and CreateDefault<Gadget>() both compile and
run, constructing a genuine new instance of whichever type was
requested.

WHY THIS WORKS AS AN ANSWER
------------------------------
This implements the exact new()-constrained generic factory the
chapter introduces, calling it successfully with two different types,
directly demonstrating the capability java2-1's own Challenge 2 named
as impossible under Java's erasure.