Generics - ? extends String

[Lidija Sketa]

This is from etattva exam:

List <? extends String> list = new ArrayList <String > ();
for ( Object o : list )
{
System.out.println(o);
}

Since String is final - how can this compile?

I was under the impression it's not possible to use ? extends with final classes since no class can extend them.

This is also stated in the topic here.

[Jamie MacDonald]

When you use <? extends MyClass>, the specific class replacing the generic must pass the is-a MyClass test. In your specific case, String is-a String. Since String can't be subclassed, the list in question must always be a list of String. So technically it's legal java, just really bad coding style.

[Lidija Sketa]

I thought the compiler should check that the class is not final but that's obviously not the case.

Thanks Jamie.