how do you access and use an XML document (that is, a file containing XML-tagged data) through the Java programming language?
One way to do this, perhaps the most typical way, is through parsers that conform to the Simple API for XML (SAX) or the Document Object Model (DOM). Both of these parsers are provided by Java API for XML Processing (JAXP). Java developers can invoke a SAX or DOM parser in an application through the JAXP API to parse an XML document — that is, scan the document and logically break it up into discrete pieces. The parsed content is then made available to the application. In the SAX approach, the parser starts at the beginning of the document and passes each piece of the document to the application in the sequence it finds it. Nothing is saved in memory. The application can take action on the data as it gets it from the parser, but it can’t do any in-memory manipulation of the data. For example, it can’t update the data in memory and return the updated data to the XML file.