about analyzer

[Madhu Satyanarayana Panitini]

Hai,
 
In the indexfile  method from the indexer.java file from sample chapter
in lucene in action page no. 14, In this statement
doc.add(Field.Text("contents", new FileReader(f)));  // Index file
content
 Indexing the file content and added the document to the lucent index,
which is already tokenized, I want know where it is tokenized exactly,
because I want use my own analyzer to the text, where should I add my
own analyzer. 
 
Thanks in advance
nani