From: Doug Lea <###@###.###>

* Compile attached file HashSetTest.java
* Run java -server HashSetTest java.util.HashSet 10 50000
* look at the time for line:
  Remove (absent) : 79991

* Uncomment out line 32:
            // if (j == 0) t0(s, key, size);
* run again, with time:
  Iterator.remove : 536

Times are approx time per operation in nanosec on my ultra80 using b74.

I believe the code triggering this problem is the same as that
from our first exchange (which made me remember John's mail).
It is the lines in java.util.HashMap.remove()
        Entry e = removeEntryForKey(key);
        return (e == null ? e : e.value);

The commented line above forces a few iterations early on
to execute this with e null.