Mega Code Archive
Watch What is Going On with the Observer Patterns
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import java.util.Vector;
public class TestObserver {
public static void main(String args[]) {
Database database = new Database();
Archiver archiver = new Archiver();
Client client = new Client();
Boss boss = new Boss();
database.registerObserver(archiver);
database.registerObserver(client);
database.registerObserver(boss);
database.editRecord("delete", "record 1");
}
}
interface Observer {
public void update(String operation, String record);
}
interface Subject {
public void registerObserver(Observer o);
public void removeObserver(Observer o);
public void notifyObservers();
}
class Database implements Subject {
private Vector<Observer> observers;
private String operation;
private String record;
public Database() {
observers = new Vector<Observer>();
}
public void registerObserver(Observer o) {
observers.add(o);
}
public void removeObserver(Observer o) {
observers.remove(o);
}
public void notifyObservers() {
for (int loopIndex = 0; loopIndex < observers.size(); loopIndex++) {
Observer observer = (Observer) observers.get(loopIndex);
observer.update(operation, record);
}
}
public void editRecord(String operation, String record) {
this.operation = operation;
this.record = record;
notifyObservers();
}
}
class Client implements Observer {
public Client() {
}
public void update(String operation, String record) {
System.out.println("The client says a " + operation + " operation was performed on " + record);
}
}
class Boss implements Observer {
public Boss() {
}
public void update(String operation, String record) {
System.out.println("The boss says a " + operation + " operation was performed on " + record);
}
}
class Archiver implements Observer {
public Archiver() {
}
public void update(String operation, String record) {
System.out
.println("The archiver says a " + operation + " operation was performed on " + record);
}
}
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