Hi Prasath,
get a good book (Safari online book shelf is not bad). To give you an idea:
You have 4 possibilities to work with XML:
1) Treat it as a text
string (including regular expressions) -- not recommended
2) Use a SAX parser. J2SE1.4 has one built in. The parser will fire one event for everything it encounters in the XML and you need to provide a class that handles the events
3) Use a PULL parser (like kXML). Works a little like SAX, the main difference is that you ask for the next piece instead of getting it thrown at you.Works very well also on J2ME (Phone, PDA)
4) Use a DOM parser. J2SE 1.4 has one build in. The parser builds the XML Document as a (in memory) tree and you can move around, query and update it
Good luck with your studies.
:-) stw