Java programs are made out of classes. There's nothing there except classes. Classes are containers. They hold static members and instance members. (Members are variables and methods.) Instance members collectively form the blueprint used to instantiate objects. A special kind of method look-alike is the constructor, which acts as an initialization procedure at instantiation. We practice these concepts by designing a Counter (complete with tester). We take our design further by modeling a BankAccount (just a sketch so we don't have a tester just yet. Here's a finished version of our model, also shown here (along with a tester program). We continue to hone our newly acquired skills by designing a CashRegister (complete with tester). Next we revisit the concept of local variables in this context (instance methods) and write a simple tester for that too. We say that class variables (also known as static) should be referenced via the class they belong to, and instance variables, likewise, via the instance they are part of. It follows that a special reference (this) is available and can be used for self reference in constructors and instance methods. We stop where the optional sections of the chapters start.