Design Principles

Learn the Adapter pattern: allow incompatible interfaces to work together. Convert interface of a class into another interface clients expect.

Learn the Builder pattern: construct complex objects step by step. Separate construction from representation and create objects with many optional parameters.

Learn the Command pattern: encapsulate a request as an object, allowing you to parameterize clients with different requests, queue operations, and support undo.

Learn the Composite pattern: compose objects into tree structures to represent part-whole hierarchies. Treat individual objects and compositions uniformly.

Model behaviour with combinable units so change remains explicit and testable.

Learn the Decorator pattern: attach additional responsibilities to objects dynamically. Provide a flexible alternative to subclassing for extending functionality.

Balance reuse, simplicity, and restraint to keep systems adaptable.

Learn the Factory pattern: create objects without specifying the exact class. Understand Factory Method and Abstract Factory patterns with examples.

Design for clarity first; optimise for comprehension, then extensibility.

Learn the Observer pattern: define a one-to-many dependency between objects. When one object changes state, all dependents are notified automatically.

Learn the Proxy pattern: provide a surrogate or placeholder for another object to control access to it. Understand virtual, protection, and remote proxies.

Partition systems by the decisions they protect to keep change local and safe.

Learn the Singleton pattern: ensure a class has only one instance and provide global access to it. Understand when to use it and common pitfalls.

Five guiding heuristics to keep software modular, testable, and change-ready.

Learn the Strategy pattern: define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients.

Invest in capabilities when evidence demands them, not when imagination suggests them.