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Chapter 2 : Java Essentials
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If you buy one of those do-it-yourself furniture kits, the best way to start is just to dump all of those screws, nuts, planks, widgets and tools on the floor, group them into piles of similar looking things, and then go read the first page of the instructions. Even though you don't know what all of those things do, it helps to pick them up, look them over, and group them into similar looking piles so that you become familiar with them and can recognize them in the instructions. In this chapter we dump out all the basic pieces of Java so you can become familiar with them. However, you don't need to understand yet what every single piece does. That will become clear come as we proceed through the rest of the course and as you practice by writing lots of programs. We begin with a listing of the basic elements and then outline the structure of a generic program. We proceed through the individual elements of the language beginning with the Java reserved words, or keywords. We then discuss the basic data types in Java called primitives. These are used in expressions and with various operators to make up statements. After this introduction to the basic elements, we next start to look at how to use them. Casts & Mixing section gives rules on mixing data types in an expression and how to cast, that is "convert", from a wider data type down to a more narrow type, e.g. a long to a int. Every program, even short ones, should include plenty of comments to allow not only other users to understand how your programs work but also to allow yourself to understand them when you come back to them at a later time. So a section on commenting code is included. Although more details will be given on them later, to allow you to start writing programs as soon as possible, brief discussions of strings, and console I/O are given. Then a basic application demo is presented before the exercises. This chapter includes:
The topics are mostly in a tutorial format but for some sections, such as the operators and primitives, additional material such as tables and specifications are provided for later reference. As discussed in the previous chapter, for the example and exercise codes you can use the Starter programs that we provide. In these programs you can just stick code segments into the designated areas and then compile and run them. For now you don't need to understand class, objects, and other complexities to start programming. Later, the starter programs will just provide convenient templates in which to begin coding.
Latest update: Oct. 15, 2004
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