HI,

Not every Foo is a Bar, so of course such an assignment (or even a cast)
is impossible. (Note that for a similar (but slightly more difficult)
reason the opposite cast is impossible as well.)

Ciao,
Ingo

If you know that every Foo in the foo list is a Bar, then the only way
to get a List<Bar> object is to copy all elements from one to the
other, casting as you go.

You can "cheat", but you'd likely introduce bugs.  List<Bar> bars
=(List<Bars>)(List)foos;
In general, don't do this.

This brings up the point.  If you know that every Foo in a list is a
Bar, why not start with a List<Bar> instead of List<Foo>

Even if you don't know that before a class is instantiated, there are
ways around it.

class FooHolder<T extends Foo> {
  private List<T> list;
  // ...

   public List<T> getFoos() {
       return list;
   }
   public static void main(String...args) {
       FooHolder<Bar> fh = new FooHolder<Bar>();
       // Look ma, no casting!
       List<Bar> bars = fh.getFoos();
   }
}