Setting classpath when compiling/running Java

Set the CLASSPATH environment variable to
- the directories having .class files
- the .jar files which contain relevant .class files

Then run javac and java; it will pick required the .class files from its location.

If you say

export CLASSPATH=dir1

and the .class file is dir1/dir11/abc.class, then you must say

java dir11.abc

to enable java to find abc.class.