To learn Assertion, please visit the following link:http://www.roseindia.net/javatutorials/use-assertion-in-java.shtml
The transient modifier applies to the variables only.Transient variables are not serialized. These are not stored as the persistent state of an object.
if u don't want to write sensitive information,while serialization, declare that variable as transient.It will not be written out.
Transient variables can be declared as 'final' or 'static.