Generics error messages

I wonder if anyone can shed light on what this error message means:


Name clash: The method addAll(Collection<E>) of type
SortedArrayList<E> has the same erasure as addAll(Collection<? extends
E>) of type ArrayList<E> but does not override it
SortedArrayList.java

the code looks like this:

public class SortedArrayList<E> extends ArrayList<E> implements
Cloneable {
....


public boolean addAll ( Collection<E> c )
{
sorted = false;
return super.addAll( c );
}


Is there distinction between <E> and <? extends E>?

If the underlying arrayList has a method addAll( Collection ) types
aside, why would not my method override it.?



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