FULL PRODUCT VERSION :
java version "1.5.0_03"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_03-b07)
Java HotSpot(TM) Client VM (build 1.5.0_03-b07, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows XP SP 2

A DESCRIPTION OF THE PROBLEM :
Perhaps it is documented somewhere by I cannot find it.

Is it possible to get the following to compile without warning

  From the Collections.sort() method
    public static <T> void sort(List<T> list, Comparator<? super T> c) {
        Object[] a = list.toArray();
// original
        Arrays.sort(a, (Comparator) c);
// also compile with a warning.
        Arrays.sort(a, (Comparator<? super Object>) c);



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
see previous.

Arrays.sort(a, (Comparator<? super Object>) c);
produces the warning
warning (1,1) [unchecked] unchecked cast
found: java.util.Comparator<capture of ? super T>
required: java.util.Comparator<? super java.lang.Object>


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
If you take the expected type, character for character, then the code should compile without error.


ACTUAL -
I have found "capture of" means you have to use your imagination as what should fix the problem, and can mean different things in different situations.


ERROR MESSAGES/STACK TRACES THAT OCCUR :
warning (1,1) [unchecked] unchecked cast
found: java.util.Comparator<capture of ? super T>
required: java.util.Comparator<? super java.lang.Object>


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
Another example
Say you write
    public static<K,V> void addResverse(Map<K,V> map1, Map<? extends K, ? extends V> map2) {
        Iterator<Map.Entry<? extends K, ? extends V>> iterator = map2.entrySet().iterator();
    }

The expected type in the warning is
Iterator<Map.Entry<capture of ? extends K, capture of ? extends V>>

however the type actaully expected is
Iterator<? extends Map.Entry<? extends K, ? extends V>>
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Ignore the warning if you cannot make it go away. My IDE has the option of selectively turning off a warning on a line. Perhaps this is why they do this.