Lets say your main class name is ICFun
1) First of create a Manifest file called ICFun.MF, and inside the file paste below lines
Created-By: 1.2 (Sun Microsystems Inc.)
2) Create a batch file, which will import the path of your jar file at first line, and second line will contain the jar creating command with required classes.
jar -cvfm ICFun.jar ICFun.MF *.class
You can add the class using folder, for example, folder1/*.class folder2/classes etc.
3) Now your ICFun.jar file is ready. You can run it by clicking it, or from command line.
java -jar ICFun.jar
That's what I do for my java archive creating from my class files.