Java, Java, Java

The Third Edition still takes an objects-early approach to teaching Java, with the assumption that teaching beginners the “big picture” early gives them more time to master the principles of object-oriented programming. This approach seems now to have gained in popularity as more and more instructors have begun to appreciate the advantages of the object-oriented perspective.

Object Orientation (OO) is a fundamental problem solving and design concept, not just another language detail that should be relegated to the middle or the end of the book (or course). If OO concepts are introduced late, it is much too easy to skip over them when push comes to shove in the course.

The first time I taught Java in our CS1 course I followed the same ap- proach I had been taking in teaching C and C++ — namely, start with the basic language features and structured programming concepts and then, somewhere around midterm, introduce object orientation. This approach was familiar, for it was one taken in most of the textbooks then available in both Java and C++.

One problem with this approach was that many students failed to get the big picture. They could understand loops, if-else constructs, and arith- metic expressions, but they had difficulty decomposing a programming problem into a well-organized Java program. Also, it seemed that this procedural approach failed to take advantage of the strengths of Java’s object orientation. Why teach an object-oriented language if you’re going to treat it like C or Pascal?

I was reminded of a similar situation that existed when Pascal was the predominant CS1 language. Back then the main hurdle for beginners was procedural abstraction — learning the basic mechanisms of procedure call

and parameter passing and learning how to design programs as a collec- tion of procedures. Oh! Pascal!, my favorite introductory text, was typical of a “procedures early” approach. It covered procedures and parameters in Chapter 2, right after covering the assignment and I/O constructs in Chapter 1. It then covered program design and organization in Chap- ter 3. It didn’t get into loops, if-else, and other structured programming concepts until Chapter 4 and beyond.

Today, the main hurdle for beginners is the concept of object abstraction. Beginning programmers must be able to see a program as a collection of interacting objects and must learn how to decompose programming prob- lems into well-designed objects. Object orientation subsumes both proce- dural abstraction and structured programming concepts from the Pascal days. Teaching objects-early takes a top-down approach to these three im- portant concepts. The sooner you begin to introduce objects and classes, the better the chances that students will master the important principles of object orientation.

Java is a good language for introducing object orientation. Its object model is better organized than C++. In C++ it is easy to “work around” or completely ignore OO features and treat the language like C. In Java there are good opportunities for motivating the discussion of object orien- tation. For example, it’s almost impossible to discuss GUI-based Java ap- plications without discussing inheritance and polymorphism. Thus rather than using contrived examples of OO concepts, instructors can use some of Java’s basic features — the class library, Swing and GUI components — to motivate these discussions in a natural way.