To create a jar file execute this command given below
jar cf jar-file input-file(s)
//input files are .class files and extra files you have used like music,jars etc.
For more you can see this Creating JAR files
After creation you must specify the main class using manifest.
Ways to update a jar file with manifest……
I have created a text file as manifest like aaa.txt which contains
//a new line or enter must be pressed after Mainclassname before saving
Updating a jar file with main class, you have to move the jar file to the BIN folder of JDK. Then using the command propmt executed the commands given below:
jar umf aaa.txt calender.jar
jar xvf calender.jar
Now double-click on your JAR file….