midOOP
What is the Interface Segregation Principle (ISP)?
Updated May 17, 2026
Short answer
Clients should not be forced to depend on interfaces they do not use.
Deep explanation
ISP promotes creating smaller, focused interfaces rather than large, general-purpose ones, improving modularity and reducing coupling.
Real-world example
A printer shouldn’t be forced to implement scanning functionality.
Common mistakes
- Creating large fat interfaces.
Follow-up questions
- What is a fat interface?
- How does ISP improve design?