Java API Tutorial - Java Observable.notifyObservers()

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Syntax

Observable.notifyObservers() has the following syntax.

public void notifyObservers()

Example

In the following code shows how to use Observable.notifyObservers() method.

/*from  w w w. j a  v  a2  s  . c o m*/

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(!watchedValue.equals(value)) {
         System.out.println("Value changed to new value: "+value);
         watchedValue = value;
         
         setChanged();
         notifyObservers();
      }
   }
}
class MainObserver implements Observer {

   
   public void update(Observable obj, Object arg) {
      System.out.println("Update called");
   }
}

public class Main{
  
   public static void main(String[] args) {
      ObservedObject watched = new ObservedObject("Original Value");
      MainObserver watcher = new MainObserver();

      watched.addObserver(watcher);
      watched.setValue("New Value");
   }

}

The code above generates the following result.

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