Indexing an IntField but getting SotredField from found Document

[Clemens Wyss DEV]

When I index a Document with an IntField and then find that very Document the 
former IntField is returned as StoredField. How do I determine the "original" 
fieldtype (IntField, LongField, DoubleField ...)?

Must I ?
Number number = Field.numericValue();
if( number != null )
{
  if( number instanceof Integer)
  {
    ...
  }
  else if( number instanceof Double)
  {
    ...
  }
  ....
}