Teaching inheritance concepts with Java

Abstract

In teaching object-oriented programming, teaching inheritance is the most challenging and at the same time the most crucial aspect. The interplay of dynamic binding, late-bound self-reference, subtype polymorphism and method redefinition is so complex that it is difficult for instructors to design a gentle, step-by-step introduction. Should polymorphism be introduced first? Or is code reuse better suited as an introductory motivation? The Java Programming Language adds a further aspect to this discussion: when should named interfaces be introduced? Most textbooks follow the historical development of the mechanism and cover interfaces after the discussion of abstract classes. In this paper a different approach is described: interfaces are introduced long before and in isolation from inheritance; and the discussion of inheritance is explicitly split into its two major constituents, namely subtype polymorphism and implementation inheritance. We applied this novel approach in the two introductory courses on software development (SD1 and SD2) in the newly created Bachelor of Science in Informatics curriculum at the University of Hamburg, Germany. This experience report reflects on the design rationale behind this new approach.

A Framework Profile of .NET

“…In this manner, we obtained the manageable number of 69 namespaces; see Table II. 4 In the rest of the paper, we signify grouping by "*" as in System.Web.*. Grouping is often used in discussions of .NET-also by Microsoft.…”

“…In API migration [3], framework profiles help assessing API replacement options with regard to, for example, different extensibility characteristics. Finally, framework profiles help in teaching OO architecture, design, and implementation [4].…”

Guess my object

“…Advanced topics, such as subtyping, inheritance with abstract classes, exception handling and packages, are postponed deliberately to the following course SD2 in the second semester. On the other hand, the language construct interface of Java is introduced quite early, in the middle of SD1, to allow discussion of the explicit description of class interfaces [8]. The concept of an interface is central to any kind of software development and can be illustrated well with the interfaces of (even small) objects.…”

Exploring accessibility and visibility relationships in java

“…major stumbling block in understanding existing object-oriented programs [8]. The three distinct concepts of subtyping, method redefinition, and type abstraction are often not distinguished from the general notion of inheritance by many textbooks [9], thus creating another source of confusion and lack of clarity for students.…”

“…The difficulties involved in teaching and learning inheritance are well documented in the literature [9]. Many authors and instructors attempt to explain inheritance through repeated examples of its use.…”