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
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:
- Elements - overview
of the various parts of the Java language.
- Structure - the
layout of a generic program or class.
- Keywords & Symbols
- words & symbols reserved for the Java compiler.
- Primitive Types
- the basic data types.
- Comments - how to
put comments into the Java code.
- Expressions -
elemental operations that return a value.
- Operators - all
the operations defined in Java.
- Statements - a
complete "sentence" in the code.
- Casts & Mixing
- how to deal with expressions with a mix of primitive types.
- Strings - character
strings in Java are part of the core language.
- Print Output
- a simple way to send output to the command line.
- an applet & an application (a standalone program) to
demonstrate how to send output to the console..
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
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.
syntax has much in common with C/C++. However, there are also
many differences. See a comparison of
Java vs C/C++.
Latest update: Oct. 15, 2004