| Sometimes, your programs will reference external libraries that are custom libraries of your own, or a third-party library, or a package in the Java 2 Enterprise Edition. Use the set command to set the classpath environment variable. The classpath tells the Java Virtual Machine where to find necessary class libraries. These libraries can be directories, .jar files (most commonly), .class files, or even .zip files. The path to a .jar or .zip file ends with the file name; the path to a .class file ends with the directory name . In Windows First, open a command prompt. Then type
set CLASSPATH=.;C:\java\MyClasses;C:\java\My.jar
Note that setting the classpath in this manner will only sustain the variable for the current command prompt session. Closing the prompt and opening a new one resets the variable. In Linux/UNIX In the bash shell you can type the following to set the classpath:
export CLASSPATH=/home/someapp/MyClasses.jar: $CLASSPATH
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