Programming Languages
Java
Subjective
Sep 24, 2025
Implement Observer pattern in Java.
Detailed Explanation
interface Observer {\n void update(String message);\n}\n\nclass Subject {\n private List observers = new ArrayList<>();\n \n public void addObserver(Observer observer) {\n observers.add(observer);\n }\n \n public void removeObserver(Observer observer) {\n observers.remove(observer);\n }\n \n public void notifyObservers(String message) {\n for (Observer observer : observers) {\n observer.update(message);\n }\n }\n}\n\nclass ConcreteObserver implements Observer {\n private String name;\n \n public ConcreteObserver(String name) {\n this.name = name;\n }\n \n public void update(String message) {\n System.out.println(name + " received: " + message);\n }\n}
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