Introduction to Java Programming - Building Java Programs: A Back to Basics Approach - page 8

Java also includes a large amount of prewritten software that programmers can uti-
lize to enhance their programs. Such off-the-shelf software components are often
called libraries. For example, if you wish to write a program that connects to a site
on the Internet, Java contains a library to simplify the connection for you. Java con-
tains libraries to draw graphical user interfaces (GUIs), retrieve data from databases,
and perform complex mathematical computations, among many other things. These
libraries collectively are called the Java class libraries.
Java Class Libraries
The collection of preexisting Java code that provides solutions to common
programming problems.
The richness of the Java class libraries has been an extremely important factor in
the rise of Java as a popular language. The Java class libraries in version 1.6 include
over 3750 entries.
Another reason to use Java is that it has a vibrant programmer community.
Extensive online documentation and tutorials are available to help programmers learn
new skills. Many of these documents are written by Sun, including an extensive ref-
erence to the Java class libraries called the API Specification (API stands for
Application Programming Interface).
Java is extremely platform independent; unlike programs written in many other
languages, the same Java program can be executed on many different operating sys-
tems, such as Windows, Linux, and Mac OS X.
Java is used extensively for both research and business applications, which means
that a large number of programming jobs exist in the marketplace today for skilled
Java programmers. A sample Google search for the phrase “Java jobs” returned
around 40,000,000 hits at the time of this writing.
The Java Programming Environment
You must become familiar with your computer setup before you start programming.
Each computer provides a different environment for program development, but there
are some common elements that deserve comment. No matter what environment you
use, you will follow the same basic three steps:
1. Type in a program as a Java class.
2. Compile the program file.
3. Run the compiled version of the program.
The basic unit of storage on most computers is a file. Every file has a name. A file
name ends with an extension, which is the part of a file's name that follows the
period. A file's extension indicates the type of data contained in the file. For example,
files with the extension .doc are Microsoft Word documents, and files with the
extension .mp3 are MP3 audio files.