? extends String

[Rodolfo Mendoza]

Hi guys,
Anyone knows why the following code don't work :

public void myMethod(List<? extends String> list){
  list.add("Foo");
}

The following work fine:

public void myMethod(List<String> list){
 list.add("Foo");
}

Thanks,

[Uttara Rishi]

 
public void myMethod(List<? extends String> list)
{
  list.add("Foo");
}
   

You cannot add anything to a List that uses <? extends> or <?>
You can add only when the method signature is <? super Dog?

In short

<? extends> - no adding.
<?> - you can pass anytype into the method but still no adding.
<? super> - adding allowed.

Hope that helps. Please correct me if I am wrong.

Uttara Rishi.

[Rodolfo Mendoza]

Uttara thanks
You are right...

[ahmed yehia]

You cannot add anything to a List that uses <? extends> or <?>

Thats correct but with little exception that you can add 'null'.

[Uttara Rishi]

Thanks Ahmed.