Practical utilities
The article explains how the Facade design pattern hides the intricacies of multiple subsystems—such as inventory, payment, logistics, and notification—behind a single, easy‑to‑use class, illustrating the problem, solution, code examples, relation to the Law of Demeter, real‑world usages, and common pitfalls.
The article explains how the Composite pattern solves the pain of handling tree‑like structures—such as orders with nested packages—by providing a uniform component interface that eliminates instanceof checks, discusses transparent vs safe variants, shows real‑world library examples, and outlines when the pattern is appropriate.
Adapter pattern acts as a translation layer that lets existing classes with mismatched interfaces interoperate without modification, illustrated through a logistics API integration example, with detailed object and class adapter implementations, trade‑off analysis, standard library and Spring examples, and a comparison with decorator and proxy patterns.
The article explains the Decorator pattern, showing how it dynamically adds functionality to objects without modifying them or using inheritance, using an order pricing example and Java IO streams, compares it with inheritance and Proxy, and outlines when to apply decorators effectively.
This article introduces the structural Proxy pattern, demonstrates three implementations—hand‑written static proxy, JDK dynamic proxy, and CGLIB subclass proxy—explains their mechanisms, trade‑offs, and limitations, and shows how Spring AOP selects between them for cross‑cutting concerns like logging, transactions, and caching.
The article explains the Prototype design pattern, showing how cloning existing objects can replace costly object construction, details Java’s Cloneable and clone() mechanisms, the pitfalls of shallow copying, and various deep‑copy techniques such as manual recursion, serialization, and library utilities.
The article explains why traditional telescoping constructors and JavaBean setters fail for objects with many optional fields, and demonstrates how the Builder pattern—both the simplified static inner class version and the full GoF version with a Director—provides readable, step‑by‑step assembly, mandatory validation, and immutable results, with guidance on when to apply it.
The article explains the Abstract Factory pattern by contrasting product families with product hierarchies, showing why the Factory Method fails for bundled products, presenting the pattern's structure and code, and detailing its open‑closed principle tilt and appropriate usage scenarios.
This article walks through the evolution from direct object instantiation to Simple Factory and finally to the Factory Method pattern, explaining why scattering new statements is problematic, how Simple Factory centralizes creation but still violates the Open/Closed principle, and how the Factory Method delegates the decision to specialized factories, complete with code examples, role definitions, and guidance on when to apply each approach.
The article explains that design patterns rely on solid design principles—SRP, OCP, LSP, DIP, ISP, LoD, and CARP—using a flawed order‑processing example to show each principle, how to refactor the code, and why over‑engineering must be avoided.
