If another module wants to listen on the changes of property 
JarDataObject.VALID_PROP, it will typically use the following code

PropertyChangeEvent evt = ...
if (JarDataObject.VALID_PROP.equals(evt.getPropertyName())) {
   JarDataObject jarDO = (JarDataObject)evt.getSource();
   if (jarDO.allValid()) {
      ...
   }
}

However, there are two problems:
1) JarDataObject.VALID_PROP is not public, it should be public
2) jarDO.allValid() is called twice (it was running when the property change 
was fired, and it is called again in the listener), which is inefficient and 
non-scalable. There should be a method which returns the validity of the jarDO 
without recomputing it.

This issue blocks BugTraq issue 4467437.