JOB entry sets are backed by JOB maps. Instances
of JOB entry sets are returned by method JobMap.entrySet().
JOB entry sets may be used to created JOB iterators using one of the following methods:
Iterator iterator() JobIterator iterator(Object key)
The second method positions the cursor at the entry of the given key.
Thus, the first call JobIterator.next() or JobIterator.previous()
returns the entry of the given key.