java - Change private variable value inside interface implementation -

i'm having trouble changing value of private variable ( of class implements interface) inside interface implementation.

i have interface iclient:

public interface iclient{      void shownewarticles(article a); } 

and class client implements iclient:

public class client implements iclient{   ( .... )   private defaultlistmodel<string> listmodelarticles = new defaultlistmodel<>();   ( .... )   @override  public void shownewarticles(article a){       string infoarticle = ("["+a.getkeyword().touppercase()+"] "+a.gettitle());       listmodelarticles.addelement(infoarticle);      listarticles.setmodel(listmodelarticles);  }  } 

the problem when execute shownewarticles() method, doesn't add element in listmodelarticles, if create private or public method (inside client class ) , execute listmodelarticles.addelement(infoarticles) inside it, infoarticle inserted model correctly. access modifiers?

i found solution. problem class call the iclient method of client class. tried solve problem :)

my solution:

@override public void shownewarticles(article a) throws remoteexception {     iclient client = maincontroller.getinstance().getclient();    client.shownewarticles(a); } 

before solution:

@override public void shownewarticles(article a) throws remoteexception {    clienti.getinstance().shownewarticles(a); } 

i don't know why wasn't working before, though using singleton. works.