A generic decorator for Observable objects.

Generic Decorator

public interface Obj {
 protected void doSomething(); 
}

public class ObjImpl implements Obj {
  
  protected void doSomething() {
    int x = 5*5;
  }
  
}

public abstract class Observable {
  Set<Observer> observers;
  
  public void addObserver(Observer observer);
  
  public void removeObserver(Observer observer);
  
  public void updateObservers();
  
}

public class ObservableObj extends Observable implements Obj {
  private Obj obj;
  
  public ObservableObj(Obj obj) {
    this.obj = obj;
  }
  
  protected void doSomething() {
    super.doSomething();
    updateObservers();
  }
}


public class ObservableFactory<I> {
  public I getObservable(Class<I> observableClass);
}

Runnable observableRunnable; = getObservable(Runnable.class);
r.addObserver().run();