Design Patterns Tutorial
Creational, structural and behavioral patterns with runnable examples, and how to know when to skip them
Intermediate4 lessonsabout 27 min of reading
This course is for developers who write working code and want a shared vocabulary for solving recurring design problems, or who keep meeting the words factory, decorator and observer in interviews and code reviews without a clear picture. You should be comfortable with classes and interfaces; if not, begin with Object-Oriented Programming.
You will learn the three families of the classic catalogue through concrete problems: creational patterns that decide how objects are built (and why the singleton is controversial), structural patterns that fit existing pieces together (adapter, decorator, facade), and behavioral patterns that organise how objects cooperate (strategy, observer, command). Each lesson sticks to one language, Python or Java, and every example was run to produce the output shown.
The last lesson is the most important one: how to decide whether a pattern is worth its cost, how to recognise over-engineering, and how many patterns now live inside language features. If you are working toward design interviews, finish with System Design and the SOLID refactor.
Design Patterns lessons
- 1Creational Design Patterns: Factory, Builder and the Singleton DebateLearn the creational design patterns with Python: a registry-based factory, a validating builder, and why the singleton is controversial.7 min read
- 2Structural Design Patterns: Adapter, Decorator and Facade in JavaLearn the structural design patterns in Java: wrap a vendor class with an adapter, stack behaviour with decorators, and simplify subsystems with a facade.7 min read
- 3Behavioral Design Patterns: Strategy, Observer and Command in PythonUnderstand the behavioral design patterns in Python: swap algorithms with strategy, broadcast events with observer, and support undo and redo with command.6 min read
- 4Choosing and Avoiding Design Patterns: Over-Engineering and AlternativesLearn when to use a design pattern and when not to: spot over-engineering, apply a decision checklist, and see patterns as built-in language features.7 min read
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