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in this article were going to describe a tool that weve created to help oo newcomers understand the class/instance relationship, inheritance between classes and linking between objects...by automatically converting an object graph into html. the tool weve created is based on the "circlegram" idea used by almost every object-oriented teacher during conventional "chalk and blackboard" lessons.
our work at the computer science department of milano-bicocca university in italy is a mix of software design, programming and teaching. we use unified modeling language (uml) for design, java for programming and blackboards for teaching. when we teach, we also sometimes use overheads/slides. "so what?" you may say, "every teacher in the world does the same...."
right, but we have an added problem: we have to teach java and general oo (object-oriented) concepts to students at their very first course at the very start of their computer science career. so these students are often a complete tabula rasa — theyve had no prior programming experience whatsoever.
this happens because in italy we dont have screening or filtering at entrance: every high school student can enter almost any university, and major in whatever he or she likes. there are no formal restrictions or requirements, so a student from a high school where they specialize in greek and latin can enroll to study software engineering or physics. (students can then abandon or change studies as and when they realize their mistake, along the lines of the dor army mechanism — "dismissed on request".)
given this situation, you can just imagine how our java programming course attracts an eclectic group of students: we have students with no prior experience in using a pc, let alone programming!
the business world isnt that different. we dare say this because we also teach short java courses for programmers from a wide variety of companies. they often have prior experience in languages such as cobol, rpg, c, visual basic, and so on. sometimes (very rarely) we also meet a c++ programmer. but prior knowledge isnt always an advantage: it can be misleading when you try to map a procedural language into an object-oriented one.
in both cases (university and business), we face a major problem when teaching java and oo concepts: we call it the "class/instance problem." newcomers and experienced procedural programmers alike find it difficult to fully grasp the meaning and the difference between a class and its instances (except of course in the case of a good c++ programmer).
now of course we havent discovered anything that wasnt already known; its a problem thats be... 下一页