Java Reference
In-Depth Information
More important are the bin and lib subfolders. The lib folder contains the JAR files that hold the core classes
(e.g.,
String
). For example, if you display the contents of lib, the rt.jar file can be seen. This file contains many of the
core classes.
The bin folder holds many JRE functions. For instance, the file named java.exe in bin contains a program that
allows you to run a Java application in the JRE. However, before that can happen Windows must be configured to find
the Java support functions and core classes.
Tutorial: Environment Variables
There are many different Windows' environment variables, each with a unique name. Environment variables can be
defined as system variables—meaning that they are universal for all applications on the PC. (It is like saying that a
red traffic light is a national “driving environment variable” meaning
stop
. Regardless of where you are driving in the
nation, a red traffic light means stop.) Environment variables can also be defined as user variables. User variables are
only valid for a particular user of the computer. In addition, environment variables can be changed dynamically. This
means that a user or an application can change them temporarily. When changed dynamically, the new values are
only in effect for as long as that user or application continues processing. If another application or the same user starts
up, the variables original values are used.
One way to change environment variables values is through the Control Panel.
1.
Click the Start button and on the right side of the Start menu select Control Panel
The “All Control Panel Items” window will be displayed (see Figure
A-13
).
Figure A-13.
2.
Click System to display the “System” window (see Figure
A-14
).
