用Jar文件关闭Jar文件

When writting an updater for a program, I quickly realized that the program will have to be closed for the updater to work properly. I remember long ago as a new programmer seeing a strange peice of code that could edit variable values or call methods of a class in a second jar file. I was wondering if anyone knew of such code. If not I can figure out something else.When writting an updater for a program, I quick