# Q&A Interview Preparation Guide

## Design Decisions and UML Diagrams

### Use Case Diagram
**Question**: Explain the actors and use cases in your system.
**Answer**: The system has two main actors:
- **Event Organizer**: Can create, update, and cancel events
- **Participant (Student/Staff)**: Can register for events, view event details, and see bill calculations

The use cases include event management operations (create, update, cancel) and registration operations (register, view details, calculate fees, manage optional services).

### Class Diagram
**Question**: Explain the relationships between your classes.
**Answer**: The system uses several key relationships:
- **Inheritance**: Event is an abstract base class with concrete implementations (Seminar, Workshop, CulturalEvent, SportsEvent)
- **Composition**: Registration contains OptionalService and Discount objects
- **Association**: Event has multiple Registration objects
- **Builder Pattern**: RegistrationBuilder creates Registration objects

### Sequence Diagrams
**Question**: Walk through the event creation and registration processes.
**Answer**: 
- **Event Creation**: Organizer inputs data → GUI sends to EventManager → EventManager creates Event object → Confirmation
- **Registration**: Participant selects event → GUI validates → RegistrationManager checks capacity → Creates Registration using Builder → Calculates fees → Displays bill

## Design Pattern Justification

### Why Builder Pattern?
**Question**: Why did you choose the Builder pattern for Registration?
**Answer**: The Builder pattern was chosen because:
1. **Complex Object Construction**: Registration objects have many optional components (services, discounts)
2. **Flexibility**: Allows step-by-step construction with method chaining
3. **Future Extensibility**: New services or discounts can be added without changing existing code
4. **Readability**: Makes the construction process clear and maintainable
5. **Validation**: Ensures all required fields are set before object creation

### Alternative Patterns Considered
**Question**: What other patterns could you have used?
**Answer**: 
- **Factory Pattern**: Could create different registration types, but doesn't handle optional components well
- **Strategy Pattern**: Good for different discount calculations, but doesn't solve construction complexity
- **Composite Pattern**: Could work for services, but Builder is more appropriate for the construction process

## Object-Oriented Principles

### Inheritance
**Question**: How does your design demonstrate inheritance?
**Answer**: 
- Event hierarchy with abstract Event class and concrete subclasses
- User hierarchy with EventOrganizer and Participant extending User
- Discount hierarchy with EarlyBirdDiscount and GroupDiscount extending Discount

### Encapsulation
**Question**: How is encapsulation implemented?
**Answer**:
- Private fields with public getter/setter methods
- Builder pattern encapsulates complex construction logic
- Manager classes encapsulate business logic

### Polymorphism
**Question**: Where do you use polymorphism?
**Answer**:
- Event objects can be treated uniformly regardless of specific type
- Discount calculations use abstract method implementation
- GUI components work with Event interface without knowing specific types

### Abstraction
**Question**: How does abstraction help your design?
**Answer**:
- Abstract Event class defines common interface for all event types
- Abstract Discount class allows different discount strategies
- Manager classes abstract business logic from GUI

## Future Enhancements

### Extensibility
**Question**: How would you add new event types?
**Answer**: 
1. Create new class extending Event
2. Implement getEventType() method
3. Add to GUI event type dropdown
4. No changes needed to existing code

### New Discount Types
**Question**: How would you add a student discount?
**Answer**:
1. Create StudentDiscount class extending Discount
2. Implement calculateDiscount() and isApplicable() methods
3. Add to EventManager's available discounts
4. Builder pattern automatically handles it

### Database Integration
**Question**: How would you add database persistence?
**Answer**:
1. Create DAO (Data Access Object) classes
2. Add database operations to Manager classes
3. Implement serialization for complex objects
4. Use dependency injection for database connections

## Technical Implementation

### Error Handling
**Question**: How do you handle errors in your application?
**Answer**:
- Input validation in GUI with user-friendly error messages
- Exception handling in business logic methods
- Capacity checking before registration
- Date format validation

### Performance Considerations
**Question**: What performance optimizations did you consider?
**Answer**:
- ArrayList for efficient list operations
- Stream API for filtering operations
- Lazy loading of GUI components
- Efficient table model updates

### Testing Strategy
**Question**: How would you test this application?
**Answer**:
- Unit tests for individual classes
- Integration tests for Manager classes
- GUI testing with sample data
- Edge case testing (full capacity, invalid dates)
- User acceptance testing with real scenarios

## Code Quality

### SOLID Principles
**Question**: How does your code follow SOLID principles?
**Answer**:
- **Single Responsibility**: Each class has one clear purpose
- **Open/Closed**: New event types can be added without modifying existing code
- **Liskov Substitution**: Subclasses can replace parent classes
- **Interface Segregation**: Classes implement only needed interfaces
- **Dependency Inversion**: High-level modules don't depend on low-level modules

### Design Patterns Benefits
**Question**: What benefits did design patterns provide?
**Answer**:
- **Maintainability**: Clear structure makes code easier to understand
- **Extensibility**: New features can be added with minimal changes
- **Reusability**: Components can be reused in different contexts
- **Testability**: Separation of concerns makes testing easier

