jar (Java ARchive) file is like a zip file or tar archive that holds the
class files of a program.  Allows easier uploading (upload the one jar
file instead of the many class files that can make up a large
program).  When the program has been completed and ready to upload to
web site, create the jar file.


Make jar file:
jar cf jarfilename.jar  classfile1.class classfile2.class ...

to get all the anonymous inner classes:
jar cf MyProgram.jar MyProgram*.class      


In .html file for applet:
<applet archive="MyProgram.jar" code="MyProgram.class" width="400" height="200">
</applet>




Applications:
Make jar file that can be executed:
jar cmf manifest.txt MyProgram.jar MyProgram.class 

manifest.txt has:
  Main-Class: MyProgram                       #class that has main


Execute jar file:
java -jar MyProgram.jar