For command-line oriented environments, you should be able to do something like
java -cp progname.jar ClassNameor possibly
jre -cp progname.jar ClassName[note that there is no ".class" after ClassName]
However, you probably don't want to type that every time you want to run the program. So you'll have to put it in a shellscript, or .bat file.
For MS-DOS/ms-windows based machines, you would just pull up notepad, and put one of the above marked lines in "somefile.bat". You may have to specify the FULL path, however. Eg:
C:\Program files\javasoft\jre\1.1\jre -cp progname.jar ClassName
For unix based machines you would put one of the top-marked lines in some text file, and make it a shellscript. So,
#!/bin/sh jre -cp progname.jar ClassNameDon't forget to run "chmod 0755 textfile", on the textfile you make, so it will actually do something!
If you have a mac, look at my macintosh java page
If you have any suggestions, comments, or "hey, it works on platform xxx, cool", drop me a line!