Sharing variable among different file

Question

How to set value to a variable from different file.I can not use interface because interface make everything as final.Is there any other way to set number of variables from more than one file?

Answer 1

I guess you want to declare the variable in one class and change the value of the variable in another class. If I am correct, try the following
public class First {
        public int a = 10;
//TODO
public class Second {
     private First firstObject = null;
     public void changeValue() {
           if(firstObject == null) {
               firstObject = new First();
               firstObject.a = 30;
}