1. QmPe
initiative
OBSERVER PATTERN explained !
Prepared by Annamalai C
Copyright 2006-2011

2. Observer Pattern in Real Life
There is always a Observer and Observable object around you.
You are an Observer, TV is an Observable Object.
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Ideology of Observer Pattern is something close.
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Colloquially Observers are called as Listeners
Observables are called as Providers
Observable Observer
Copyright 2006-2011

3. Observer Pattern in Java
Observable Objects are called as Subject.
Copyright 2006-2011

4. Real Life vs Java Object
Observer
Copyright 2006-2011

5. Real Life vs Java Object
Observable
Copyright 2006-2011

6. How Observer Pattern works in Real Life ?
1
Register/ Attach
(When he wants to watch TV)
DeRegister/ DeAttach
(When he wants to not Watch TV)
Observable Observer
2
Notify
(When someone is Watching TV)
3
Observable Observer
Copyright 2006-2011

7. How Observer Pattern works in Java ?
public void changeChannel(String channelName) {
public static void main(String[] args) { this.channelName = channelName;
//Initialise Observable setChanged();
Television tv = new Television("Star Plus"); this.notifyObservers();
}
2
//Initialise Observer
TelevisionViewer tViewer = new TelevisionViewer();
//Register Observer to Observable 3
1 tv.addObserver(tViewer);
//Change TV Channel
tv.changeChannel("STAR CRICKET");
} public void update(Observable arg0, Object arg1) {
System.out.println("Channel Changed”);
}
Copyright 2006-2011

8. THANK YOU
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QmPe
initiative
Copyright 2006-2011