Question

So lets say that in my entry point class (i.e the class which runs when the program starts (which has the public static void main(String args[]) function). In that class I have this variable:

private ArrayList<String> myData=new ArrayList<String>(); 

This class instantiates another class, which needs to have access to the myData member of the entry point class. How can it retrieve this arraylist?

Edit: To clarify, in the main() method I could do this:

SomeOtherClass myClass=new SomeOtherClass(); 

and then I could do:

myClass.someMethod(); 

however, in the myClass object, how could I perform a method/retrieve something from the entry class, which instantiated the myClass object?

Answer 1

It sounds like your entry point is still static when it calls some other class, but your ArrayList is a member of an instance of it. You need to move out of the static world and into instances.

I’d refactor your main method into a private construtor, and put in a new main() which launches it as a new instance.

Note that this code is very rough, but it should serve to illustrate what you need to do.

public class EntryPoint {     private ArrayList<String> myData=new ArrayList<String>();      public static void main( String[] args ) {         EntryPoint ep = new EntryPoint();         ep.init();     }      private void init() {         // Populate myData perhaps?          SomeOtherClass myClass=new SomeOtherClass();         myClass.someMethod( this );     }      public List<String> getMyData() {         return myData;     } }     public class SomeOtherClass {     public void someMethod( EntryPoint entry ) {         List<String> data = entry.getMyData();         // do stuff with data..!     } }