title: Global variable in Java with access to it in any class in a package
body: <p>I have a package with different classes. One class implements a structure data. I want to use an instance of this class as a global variable in all the classes of my package. How can I use and modify this variable, remaining its content. </p>
  
  <p>Creating a static variable is not what I need, because I need to modify it, not just read it.</p>