As you've learned in this chapter, even when the application is mostly done, still a bit of work can be left to do.
Credit card authorization requires integrating into a third-party application—luckily, this is an easy process because most authorization companies have simple Java-based interfaces. You might also need to integrate into existing accounting, shipping, or inventory systems. You also need to consider database integrity issues during critical “two-phase” operations, such as charging credit cards and then recording an order.
Finishing an application also involves making sure that the code is commented as appropriate and that Javadoc has been written for any externally visible methods.