A Exception that collects a Set of child Exceptions together. Typically thrown after a loop, with all of the exceptions thrown during that loop, but delayed so that the loop finishes executing.

class UmbrellaException implements Exception {

 /**
  * A message describing the format error.
  */
 Set<Exception> _causes;

 UmbrellaException(this._causes) {
   throw (makeCause(_causes));
 }

 Set<Exception> get causes => _causes;

 String toString() => makeMessage(_causes);

 static String makeMessage(Set<Exception> causes) {
   if (causes.length == 0) {
     return null;
   }

   StringBuffer b = new StringBuffer();
   for (Exception t in causes) {
     if (b.length > 0) {
       b.write("; ");
     }
     b.write(t.toString());
   }

   return b.toString();
 }

 static Exception makeCause(Set<Exception> causes) {
   Iterator<Exception> iterator = causes.iterator;
   if (!iterator.moveNext()) {
     return null;
   }

   return iterator.current;
 }


}