What is SOLID? Which principle is your favorite?

SOLID is a set of five principles of object-oriented programming aimed at creating flexible and maintainable code:

• S (Single Responsibility Principle) — the principle of single responsibility
• O (Open/Closed Principle) — the principle of openness/closure
• L (Liskov Substitution Principle) — the Liskov Substitution Principle
• I (Interface Segregation Principle) — the principle of interface segregation
• D (Dependency Inversion Principle) — the principle of dependency inversion

The most favorite principle is the Single Responsibility Principle, as it helps create modules that are easy to test and maintain, reducing code coupling.