A Personalized BMI Calculator

The (classes of the) objects we saw in the previous chapter are rather simple. Not because they are small in size. In fact, in well-written, real-world code, objects tend to be fairly small. The main reason for the simplicity is that each of these objects has a single, self-contained method that does not interact with other methods. In this chapter we will see how methods can call each other, much like we humans delegate work to others. Such collaborative methods do not increase the complexity of the kind of applications we build. Instead they improve the style of the program, making it easier to understand, change, debug, and get correct. We will see some additional elements of programming style such as named constants and comments. Writing complex collaborative methods often requires to break the application development process into phases in which we first develop the high-level steps that decide what the computer should do and phases in which we translate these steps into code in some programming language such as Java. We will look also at this stepwise refinement process.