Swing UIDefaults is an Hashtable. But its Set interface is utterly unusable.

<code>
UIDefaults udf = UIManager.getDefaults(); //udf.size() returns 568
Set defs = udf.entrySet(); //defs.size() returns 0 !!
Iterator itr = defs.iterator(); //so, this code doesn't work
while (itr.hasNext()){
 Map.Entry mentry = (Map.Entry)(itr.next());
 System.out.println
  (mentry.getKey().toString() + " : " + mentry.getValue().toString());
} /* keySet() and values() also don't work */
</code>

After three days/nights struggle, I've found a solution on this forum which
uses old Enumeration interface instead of Set.

<code>
.....
Enumeration enm = udf.keys();
while (enm.hasMoreElements()){
 Object key = enm.nextElement();
 Object value = udf.get(key);
 .....
} /*This code perfectly works !!*/
</code>

Then, you might see my question in the post subject line.
Why on earth the Set interface doesn't work for UIDefaults which is
an Hashtable?