public interface Locator—Interface for associating a SAX event with a document location.
If a SAX parser provides location information to the SAX application, it does so by implementing this interface and then passing an instance to the application using the document handler's setDocumentLocator method. The application can use the object to obtain the location of any other document handler event in the XML source document.
Note that the results returned by the object will be valid only during the scope of each document handler method: The application will receive unpredictable results if it attempts to use the locator at any other time.
SAX parsers are not required to supply a locator, but they are very strongly ...