A DESCRIPTION OF THE PROBLEM :
The documentation of the generic class AbstractList<E> as a whole contains these two texts:
set(int index, Object element)
add(int index, Object element)

Only a few lines below, those methods are referenced in their new (correct) form:
set(int index, E element)
add(int index, E element)


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
  To implement a modifiable list, the programmer must additionally override the set(int index, E element) method (which otherwise throws an UnsupportedOperationException. If the list is variable-size the programmer must additionally override the add(int index, E element) and remove(int index) methods.
ACTUAL -
  To implement a modifiable list, the programmer must additionally override the set(int index, Object element) method (which otherwise throws an UnsupportedOperationException. If the list is variable-size the programmer must additionally override the add(int index, Object element) and remove(int index) methods.

URL OF FAULTY DOCUMENTATION :
http://download.java.net/jdk6/docs/api/java/util/AbstractList.html