Stateless Session Beans:
A stateless session bean does not maintain a conversational state with the client. When a client invokes the methods of a stateless bean, the instance of bean variables may contain a state specific to that client only for the duration of a method invocation. Once the method is finished, the client-specific state should not be retained i.e. the EJB container destroys a stateless session bean.
These types of session beans do not use the class variables (instance variables). So they do not persist data across method invocation and therefore there is no need to passivates the bean's instance. Because stateless session beans can support multiple clients, they provide the better scalability for applications that require large numbers of clients.
For read more information,Tutorials and Examples on EJB visit to :http://roseindia.net/ejb/http://roseindia.net/ejb/examples-of-StatelessBean.shtml