Project Android with Custom Library + Global var -

i creating book , i'm interested in globalizing variables (objects).

in 1 project can singletone: if use in library , give value, if in project consult value 0.

library:

public class globals{    private static globals instance;     // global variable    private int data;     // restrict constructor being instantiated    private globals(){}     public void setdata(int d){        this.data=d;    }    public int getdata(){      return this.data;    }     public static synchronized globals getinstance(){      if(instance==null){          instance=new globals();      }      return instance;    }    /*then write methods here*/       public void yourmethod(){} } 

library: class examplelib

globals g = globals.getinstance();         g.setdata(120)); 

myproject

globals g = globals.getinstance();         system.out.println(g.getdata()); // show 0