Implementing a Simple Event Notifier

In this section, you will learn how to implement a Simple Event Notifier.

Ads

Tutorials   
How to read properties file in Java? Generate random numbers in Java Cloneable Interface in Java What is the flaw with the Stack class? List In Java Java Stack Example HashSet In Java Enumeration in java How to generate random number in java Iterator in java Queue in java Transient Java Keyword clone method in Java Java Queue example Logger in Java Java current date - How to get current date in Java Collection : LinkedList Example Collection : ArrayList Example Random alpha numeric string of fixed size Java List Iterator Example The Hashtable Class The BitSet class Java Vector Java Enumeration Data Structures in Java Java Transient Variable Java Date Format Example Java Properties File Example Map.Entry Java Interface Java Property File java preferences,Change the value of Preferences by user Retrieving a Preference Node Java hasNext Write Keys and Values to the Properties file in Java Get All Keys and Values of the Properties files in Java Properties file in Java Properties file in Java Determining If a Preference Node Contains a Specific Value Change the value of Preferences by user Clone method example in Java Implementing a Simple Event Notifier Determining When a Preference Node Is Added or Removed Listening for Changes to Preference Values in a Preference Node Importing Preferences Finding a Preference in a Preference Tree Retrieving the Parent and Child Nodes of a Preference Node Determining If a Preference Node Exists Removing a Preference Node Creating a Preference Node Getting the Maximum Size of a Preference Key and Value
Ads

Implementing a Simple Event Notifier

     

In this section, you will learn how to implement a Simple Event Notifier. 

The Observer and Observable classes are useful for implementing a simple event notifier. The Observer class informed the changes that occurred in observable objects and Observable class represents an object that the application wants to have observed. You can see in the given example, the setChanged() protected method marks the Observable object as having been changed.  If this object has changed, then notify all of its observers using the protected method notifyObservers(Object args) passing object type parameter. The method update(Observable o, Object arg) is called whenever the observed object is changed. When you call the method my.setChanged(), it will indicate that the model has changed. Then the event is fired displaying the updated argument.

Here is the code of SimpleEventNotifier.java  

import java.util.*;
class MyClass extends Observable {
  public synchronized void setChanged() {
  super.setChanged();
  }
  public synchronized void notifyObservers(Object args){
  System.out.println(args);
  }
  }
  public class SimpleEventNotifier{
  public static void main(String[]args){
  MyClass my = new MyClass();
  my.addObserver(new Observer() {
  public void update(Observable o, Object arg) {
  }
  });
  my.setChanged();
  Object arg = "Event is fired";
  my.notifyObservers(arg);
}
}

Output will be displayed as:

Download Source Code:

Advertisements

Share on Google+Share on Google+

Implementing a Simple Event Notifier

Posted on: January 12, 2009 If you enjoyed this post then why not add us on Google+? Add us to your Circles

Advertisements

 

Discuss: Implementing a Simple Event Notifier  

Post your Comment


Your Name (*) :
Your Email :
Subject (*):
Your Comment (*):
  Reload Image
 
 
Comments:0

Ads

 

Ads