Question

I have a class:

public class SomeClass <TView extends View>{

    private TView tv;

    public SomeClass(View v){
        tv=(TView) v; //unchecked cast warning
    }

}

View is a concrete class (not abstract, not interface).

Question is

Why do I get an unchecked cast warning, even if TView extends View?

Answer 1

The cast is not enforced at runtime.

Your class post-erasure looks like:

public class SomeClass {

    private View tv;  // Post-erasure, TView -> View

    public SomeClass(View v){  // Post-erasure, TView -> View
        tv=(View) v; //unchecked cast warning due to cast of View to View
    }

}

Note that post-erasure, the constructor is casting a value of type View to type View since that is the lower-bound for <TView extends View>.

Casting View to View does not check anything at runtime, which is why you get the warning.