Java.util.Observable.deleteObserver() Method

Description

The java.util.Observable.deleteObserver(Observer o) method deletes the specified observer o from the set of observers of this object.

Declaration

Following is the declaration for java.util.Observable.deleteObserver() method

public void deleteObserver(Observer o)

Parameters

• o -- The observer to be deleted from the set of observers.

Return Value

Exception

Example

The following example shows the usage of java.util.Observable.deleteObserver(Observer) method.

package com.tutorialspoint;

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(value);
      }
   }
}
public class ObservableDemo implements Observer {
   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();

      // trigger value change
      watched.setValue("Value before addObserver");
      // add observer to the watched object
      watched.addObserver(watcher);
      // trigger value change
      watched.setValue("Value after addObserver");
      // delete observer
      watched.deleteObserver(watcher);
      // trigger value change
      watched.setValue("Value after deleteObserver");
   }
   
   public void update(Observable obj, Object arg) {
      System.out.println("Update called with Arguments: "+arg);
   }
}

Let us compile and run the above program, this will produce the following result:

Value changed to new value: Value before addObserver
Value changed to new value: Value after addObserver
Update called with Arguments: Value after addObserver
Value changed to new value: Value after deleteObserver