SomeFragment.java

public class SomeFragment {

  private AdvancedInteractions advancedInteractions;

  public AdvancedInteractions advanced() {
    if(advancedInteractions == null) {
      advancedInteractions = new AdvancedInteractions();
    }
    return advancedInteractions;
  }

  public class AdvancedInteractions {
  }
}