Java Reference
In-Depth Information
more than 70,000 ideographs ( an ideograph is a graphical symbol, sometimes called an ideogram). Surrog-
ates are used to represent characters that are not contained within the basic multilingual set that is defined
by 16-bit characters.
SUMMARY
In this chapter you've looked at the basic characteristics of Java, and how portability between different com-
puters is achieved. I have also introduced you to the elements of object-oriented programming. There are
bound to be some aspects of what I've discussed that you don't feel are completely clear to you. Don't worry
about it. Everything I have discussed here I revisit again in more detail later in the topic.
• WHAT YOU LEARNED IN THIS CHAPTER
TOPIC
CONCEPT
Applets and
Applications
Java applets are programs that are designed to be embedded in an HTML document. Java applications are
standalone programs. Java applications can be console programs that only support text output to the com-
mand line, or they can be window-based applications with a GUI.
Object-Ori-
ented Pro-
grams
Java programs are intrinsically object-oriented. Object-oriented programs are implemented in terms of
problem-specific types of data rather that primitive types such as characters and numerical values.
Classes
A class is a definition of a particular type of object. A class contains specifications for the type of data
needed to define an object of the type and defines the operations that you can carry out on objects.
Class Meth-
ods
A class method is a block of code within a class definition that specifies an operation for an object of the
class type.
ConstructorsA constructor is a special kind of method within a class definition that can create objects of the class type.
Java Source
Files
Java source code is stored in files with the extension
.java.
Compiled
Java Code
Java programs are compiled to bytecodes, which are instructions for the .JVM. The JVM is the same on
all the computers on which it is implemented, thus ensuring the portability of Java programs.
Java Object
Code Files
Java object code is stored in files with the extension
.class
.
Java Pro-
gram Exe-
cution
Java programs are executed by the Java interpreter, which analyzes the bytecodes and carries out the op-
erations they specify.
Unicode
Unicode is a 16-bit character encoding that enables multiple national language character sets to be sup-
ported. Java source programs are represented internally as Unicode and Java supports programming ap-
plications with multilingual capability.
RESOURCES
You can download the source code for the examples in this topic from
www.wrox.com
.
