How to write the code for listeners in TestNG?

I want to know how can i use listeners in my java code? Also what changes are to made in the xml file if i want to incorporate the listeners? I added org.testng.ITestNGListener then too the program is throwing e开发者_运维知识库rrors?

Do you have any specific questions that are not covered by the documentation:

http://testng.org/doc/documentation-main.html#logging

?