The main purpose of the HelloWorldSession example was to get you familiar with the overall structure of a session bean. Writing three different Java files for a single component seems overwhelming at first, but after you're used to it, it doesn't seem like such a big deal.
Now that you're familiar with the structure of a session bean, you can write a bean that does some work. Specifically, you can write a bean that retrieves data from a database. For this example, assume that you have an SQL table containing product codes and prices, created using the following SQL statement:
create table price (product_code varchar(10) not null primary key, price decimal(10,2) not null)
The Pricing session bean gives ...