title: How do I make sure only one instance of my program can be executed?
body: <p>I want my program, a Java executable .jar, to be run just once. I made a program but now I want users not to be able to open more than one instance ....thanks for your time...</p>
  
  <p>I've checked the server/client solution and the lock file, but I don't understand them much, I also tried to make them run in NetBeans, with no luck...</p>