Java: cast collection type to subtype [duplicate]

Answer 1

A way to retain some type safety with minimum impact on performance is to use a wrapper. This example is about Collection, the List case would be very similar and maybe one day I'll write that too. If someone else comes before me, please let's share the code.

Answer 2

List<A> is not a subtype of List<B>!

The JLS even mentions that explicitly:

Subtyping does not extend through generic types: T <: U does not imply that C<T> <: C<U>.

Answer 3

You can cast through the untyped List interface:

List<A> a = new ArrayList<A>();
List<B> b = (List)a;

Answer 4

You can try this :

List<A> a = new ArrayList<A>();
List<B> b = (List<B>) (List<?>) a;

It is based on the answer of jarnbjo, but on don't use raw lists.