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JavaIntermediate#design-patterns
JavaIntermediate#design-patterns
What is the Observer pattern?
A behavioral pattern where an object (subject) maintains a list of dependents (observers) and notifies them automatically of state changes, commonly used for event-driven systems like GUI listeners or pub/sub systems.
Example
interface Observer { void update(String event); }
class EventBus {
List<Observer> observers = new ArrayList<>();
void notifyAll(String event) { observers.forEach(o -> o.update(event)); }
}