Common Patterns in Java
Common patterns include Factory, Builder, Strategy, Adapter, Decorator, Observer, Template Method, Command, and State.
interface PricingStrategy {
long price(Order order);
}
final class RegularPricing implements PricingStrategy {
public long price(Order order) {
return order.subtotal();
}
}
Strategy is polymorphism used to select interchangeable behavior. Builder helps construct complex immutable objects. Adapter translates one interface into another. Decorator adds behavior without modifying the wrapped implementation.
Key Takeaways
- Patterns are reusable design ideas, not mandatory class structures.
- Strategy uses polymorphism to vary behavior.
- Prefer the simplest design that remains easy to change.