Java Unboxing and Null

While playing with boxing/unboxing in Java 5, I found an interesting case. If my collection has a null value, the unboxing fails with a NullPointerException at runtime. Here is an example

  Set s = new HashSet();
  for (int i=0; i < 10; i++) {
   s.add(i);
  }
  s.add(null);
  
  System.out.println("s: " + s);
  // this is a problem. The unboxing does not handle null
  for (int sx : s) {
   System.out.println("sx: " + sx);
  }

The output of the progam is here:

s: [2, 4, null, 9, 8, 6, 1, 3, 7, 5, 0]
sx: 2
sx: 4
Exception in thread "main" java.lang.NullPointerException
 at com.mykola.TestSets.main(TestSets.java:21)

So, unboxing is fine, unless a collection has a null element.