java,design pattern,observer

import java.util.Observable;
import java.util.Observer;

class ObservedObject extends Observable {
   private String watchedValue;
   
   public ObservedObject(String value) {
      watchedValue = value;
   }
   
   public void setValue(String value) {
      // if value has changed notify observers
      if(!watchedValue.equals(value)) {
         System.out.println("Value changed to new value: "+value);
         watchedValue = value;
         
         // mark as value changed
         setChanged();
         // trigger notification
         notifyObservers();
      }
   }
}
public class ObservableDemo implements Observer {
   public String name;
   public ObservableDemo(String name) {
      this.name = name;
   }
   
   public static void main(String[] args) {
      // create watched and watcher objects
      ObservedObject watched = new ObservedObject("Original Value");
      // watcher object listens to object change
      ObservableDemo watcher = new ObservableDemo("Watcher");

      // add observer to the watched object
      watched.addObserver(watcher);
      // trigger value change
      watched.setValue("New Value");
   }
   
   public void update(Observable obj, Object arg) {
      System.out.println("Update called");
   }
}

Value changed to new value: New Value
Update called