Report the start of DTD declarations, if any.
This method is intended to report the beginning of the DOCTYPE declaration; if the document has no DOCTYPE declaration, this method will not be invoked.
All declarations reported through {@link org.xml.sax.DTDHandler DTDHandler} or{@link org.xml.sax.ext.DeclHandler DeclHandler} events must appearbetween the startDTD and {@link #endDTD endDTD} events.Declarations are assumed to belong to the internal DTD subset unless they appear between {@link #startEntity startEntity}and {@link #endEntity endEntity} events. Comments andprocessing instructions from the DTD should also be reported between the startDTD and endDTD events, in their original order of (logical) occurrence; they are not required to appear in their correct locations relative to DTDHandler or DeclHandler events, however.
Note that the start/endDTD events will appear within the start/endDocument events from ContentHandler and before the first {@link org.xml.sax.ContentHandler#startElement startElement}event.
@param name The document type name.
@param publicId The declared public identifier for theexternal DTD subset, or null if none was declared.
@param systemId The declared system identifier for theexternal DTD subset, or null if none was declared.
@exception SAXException The application may raise anexception.
@see #endDTD
@see #startEntity