Setup Java Path and classpath (from the java™ tutorials essential classes - the platform environment)

This section explains how to use the PATH and CLASSPATH environment variables on Microsoft
Windows, Solaris, and Linux. Consult the installation instructions included with your installation
of the Java Development Kit (JDK) software bundle for current information.
After installing the software, the JDK directory will have the structure shown below.
The bin directory contains both the compiler and the launcher.

Update the PATH Environment Variable (Microsoft
Windows)
You can run Java applications just fine without setting the PATH environment variable. Or, you
can optionally set it as a convenience.
Set the PATH environment variable if you want to be able to conveniently run the executables
(javac.exe, java.exe, javadoc.exe, and so on) from any directory without having to type
the full path of the command. If you do not set the PATH variable, you need to specify the full
path to the executable every time you run it, such as:
C:Javajdk1.7.0binjavac MyClass.java

The PATH environment variable is a series of directories separated by semicolons (;).
Microsoft Windows looks for programs in the PATH directories in order, from left to right. You
should have only one bin directory for the JDK in the path at a time (those following the first
are ignored), so if one is already present, you can update that particular entry.
The following is an example of a PATH environment variable:
C:Javajdk1.7.0bin;C:WindowsSystem32;C:Windows;C:WindowsSystem32Wbem

It is useful to set the PATH environment variable permanently so it will persist after rebooting.
To make a permanent change to the PATH variable, use the System icon in the Control Panel.
The precise procedure varies depending on the version of Windows:
Windows XP

1. Select Start, select Control Panel. double click System, and select the Advanced tab.
2. Click Environment Variables. In the section System Variables, find the PATH
environment variable and select it. Click Edit. If the PATH environment variable does not
exist, click New.
3. In the Edit System Variable (or New System Variable) window, specify the value of the
PATH environment variable. Click OK. Close all remaining windows by clicking OK.

Windows Vista:
1. From the desktop, right click the My Computer icon.
2. Choose Properties from the context menu.
3. Click the Advanced tab (Advanced system settings link in Vista).
exist, click New.

Windows 7:
1. From the desktop, right click the Computer icon.
2. Choose Properties from the context menu.
3. Click the Advanced system settings link.
exist, click New.

Note: You may see a PATH environment variable similar to the following when editing it from
the Control Panel:
%JAVA_HOME%bin;%SystemRoot%system32;%SystemRoot%;%SystemRoot%System32Wbem

Variables enclosed in percentage signs (%) are existing environment variables. If one of these
variables is listed in the Environment Variables window from the Control Panel (such as
JAVA_HOME), then you can edit its value. If it does not appear, then it is a special environment

variable that the operating system has defined. For example, SystemRoot is the location of
the Microsoft Windows system folder. To obtain the value of a environment variable, enter the
following at a command prompt. (This example obtains the value of the SystemRoot
environment variable):
echo %SystemRoot%

Update the PATH Variable (Solaris and Linux)
You can run the JDK just fine without setting the PATH variable, or you can optionally set it as
a convenience. However, you should set the path variable if you want to be able to run the
executables (javac, java, javadoc, and so on) from any directory without having to type the
full path of the command. If you do not set the PATH variable, you need to specify the full path
to the executable every time you run it, such as:
% /usr/local/jdk1.7.0/bin/javac MyClass.java

To find out if the path is properly set, execute:
% java -version

This will print the version of the java tool, if it can find it. If the version is old or you get the
error java: Command not found, then the path is not properly set.
To set the path permanently, set the path in your startup file.
For C shell (csh), edit the startup file (~/.cshrc):
set path=(/usr/local/jdk1.7.0/bin )

For bash, edit the startup file (~/.bashrc):
PATH=/usr/local/jdk1.7.0/bin:
export PATH

For ksh, the startup file is named by the environment variable, ENV. To set the path:
export PATH

For sh, edit the profile file (~/.profile):
export PATH

Then load the startup file and verify that the path is set by repeating the java command:

For C shell (csh):
% source ~/.cshrc
% java -version

For ksh, bash, or sh:
% . /.profile
% java -version

Checking the CLASSPATH variable (All platforms)
The CLASSPATH variable is one way to tell applications, including the JDK tools, where to look
for user classes. (Classes that are part of the JRE, JDK platform, and extensions should be
defined through other means, such as the bootstrap class path or the extensions directory.)
The preferred way to specify the class path is by using the -cp command line switch. This
allows the CLASSPATH to be set individually for each application without affecting other
applications. Setting the CLASSPATH can be tricky and should be performed with care.
The default value of the class path is ".", meaning that only the current directory is searched.
Specifying either the CLASSPATH variable or the -cp command line switch overrides this
value.
To check whether CLASSPATH is set on Microsoft Windows NT/2000/XP, execute the following:
C:> echo %CLASSPATH%

On Solaris or Linux, execute the following:
% echo $CLASSPATH

If CLASSPATH is not set you will get a CLASSPATH: Undefined variable error (Solaris or Linux)
or simply %CLASSPATH% (Microsoft Windows NT/2000/XP).
To modify the CLASSPATH, use the same procedure you used for the PATH variable.
Class path wildcards allow you to include an entire directory of .jar files in the class path
without explicitly naming them individually. For more information, including an explanation of

class path wildcards, and a detailed description on how to clean up the CLASSPATH
environment variable, see the Setting the Class Path [1] technical note.
1. http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.html

Setup Java Path and classpath (from the java™ tutorials essential classes - the platform environment)

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