英文文摘

Why has object-oriented programming had such a sweeping impact on the software development communityObject-oriented programming appeals at multiple levels. For managers, it promises faster and cheaper development and maintenance. For analysts and designers, the modeling process becomes simpler and produces a clear, manageable design. For programmers, the elegance and clarity of the object model and the power of object-oriented tools and libraries makes programming a much more pleasant task, and programmers experience an increase in productivity. Everybody wins, it would seem.

If there’s a downside, it is the expense of the learning curve. Thinking in objects is a dramatic departure from thinking procedurally, and the process of designing objects is much more challenging than procedural design, especially if you’re trying to create reusable objects. In the past, a novice practitioner of object-oriented programming was faced with a choice between two daunting tasks:

Choose a language such as Smalltalk in which you had to learn a large library before becoming productiveChoose C++ with virtually no libraries at all, and struggle through the depths of the language in order to write your own libraries of objects.

It is, in fact, difficult to design objects well ? for that matter, it’s hard to design anything well. But the intent is that a relatively few experts design the best objects for others to consume. Successful OOP languages incorporate not just language syntax and a compiler, but an entire development environment including a significant library of well-designed, easy to use objects. Thus, the primary job of most programmers is to use existing objects to solve their application problems. The goal of this chapter is to show you what object-oriented programming is and how simple it can be.

This chapter will introduce many of the ideas of Java and object-oriented programming on a conceptual level, but keep in mind that you’re not expected to be able to write f