Having designed the system, we proceed to the implementation stage. In this step, we use the class structures produced by the design to implement a system that behaves in the manner specified by the model. During this process, the programmer should follow good coding and testing practices. Although we mention some of these principles here, we do not spend a significant amount of time on them, since these are concepts common to all software implementations. Our implementation will be carried out in Java. Any new language concepts that need elaboration are dealt with in the context where we employ them.