Basic Code Design


Stoyan Stoyanov


WeltN24 GmbH


  • inspecting production incidents leads often to reading code which is not good designed
  • avoiding technical debts in the future ($)
  • you build it, you run it


  • no bashing
  • continuous learning/improving
  • more fun and time for the important things

Patterns in our codebase

  • OOP?
  • tight coupling
  • no space to move

SOLID Principles

  • Single Responsibility
  • Open-Closed
  • Liskov Substitution
  • Interface Segregation
  • Dependency Inversion
  • DRY
  • Law of Demeter

Single Responsibility

  • A class should be responsible for only one thing
    • everything in the class is highly related to its purpose
  • enforce this everywhere (functions, services)
  • "What does a Mr. Function do?"
    • BAD: computes that AND that AND that AND AND that AND that AND that ...
    • GOOD: no AND

The purpose of software engineering is to control complexity, not to create it.

Pamela Zave


Single Responsibility

  • Why it matters:
    • code is easy to understand (wow)
    • encourages code reuse
    • code can be tested
    • code can be easily refactored
    • no need of comments
      • please stop writing comments, write functions instead


Liskov Substitution

Interface Segregation

Dependency Inversion

Law of Demeter

  • Only talk to your immediate friends
  • Don't talk to strangers
  • It's a design smell
return xml.getXML().getBooks().getBookArrary(0).getBookHeader().getBookCategory();

More from the kitchen

  • Always go for the most simple solution
    • at the third refactoring you have it
  • Deep hierarchies are evil
    •   nobody understands them
  • Don't reinvent the wheel (know what's there)
    • don't write own monitoring systems or
    • own build tool or
    • own stress testing tool or
    • the new Spring-Framework or
    • own HA-Tools ..


  • Adopt design patterns
    • every week one can present a new pattern in his favorite language
  • If you think you need more time to implement the feature better, say it and fight for it.
  • Java/Js best practices every week
  • Open-Source projects

Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.

John Woods


Basic Code Design

By Stoyan Stoyanov

Basic Code Design

  • 1,149