How do you convert a source code back to a jar file?

Does anyone happen to know how to convert a source code into a Jar file would need some help, because I got a source code for a Minecraft server because I have to convert again.

"Back"?

Source code is the source, .class is the result.

.jar is an archive of .class.

You compile source code with a compiler. For java usually javac.exe from the JDK. For this to work, all files that are to be accessed directly at runtime must be visible to javac.

In the JDK is also the program "jar.exe", with which you can pack class files back into a JAR.

Development environments like Eclipse provide a more convenient way to do this because javac.exe and jar.exe are console programs that you control with cmd.exe.

Have fun.

Thank you