with notifications coupling is reduced

ProcessOrder.java

public class ProcessOrder {
    private EventPublisher eventPublisher;
    
    // ... code omitted for brevity
    
    public void execute() {
        // business logic to process an order (code omitted for brevity)
        // ...
        
        // notification of the event that an order has been processed
        eventPublisher.publish(createOrderProcessedEvent());
    }

    // ... code omitted for brevity
}