Interface Segregation Principle in LLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Interface Segregation Principle (ISP)?

ISP means that no client should be forced to depend on methods it does not use. It encourages creating small, specific interfaces rather than large, general ones.

beginner

Why is it bad to have fat interfaces?

Fat interfaces make clients depend on methods they don't need, leading to unnecessary complexity and harder maintenance.

beginner

Give a real-life example of the Interface Segregation Principle.

Think of a remote control with many buttons. If you only want to change channels, you shouldn't have to learn how to use the volume or settings buttons. Separate remotes for different functions follow ISP.

intermediate

How does ISP improve system design?

ISP improves flexibility, reduces side effects from changes, and makes code easier to understand and test by keeping interfaces focused.

intermediate

What is a common sign that an interface violates ISP?

When a class implementing the interface has to leave some methods empty or throw errors because they are not relevant to it.

What does the Interface Segregation Principle recommend?

A Use many small, specific interfaces

B Use one large interface for all clients

C Avoid interfaces altogether

D Combine unrelated methods in one interface

ISP encourages small, focused interfaces so clients only depend on what they need.

Which problem indicates a violation of ISP?

A Clients implement methods they never use

B Interfaces have too few methods

C Classes have too many dependencies

D Methods have too many parameters

If clients implement unused methods, the interface is too broad, violating ISP.

How does ISP affect code maintenance?

A Makes it harder by adding more interfaces

B Makes it easier by reducing unnecessary dependencies

C Has no effect on maintenance

D Requires rewriting all classes often

Smaller interfaces reduce side effects and simplify changes, easing maintenance.

Which analogy best explains ISP?

A A Swiss Army knife with many tools

B A single key for all locks

C A toolbox with all tools mixed

D A TV remote with only volume buttons for volume control

A remote with only needed buttons matches ISP by providing focused interfaces.

What is a benefit of following ISP?

A Interfaces become very large

B All clients share the same interface

C Clients depend only on methods they use

D Classes implement many unrelated methods

ISP ensures clients depend only on relevant methods, improving design.

Explain the Interface Segregation Principle and why it matters in system design.

Think about how forcing clients to use unused methods can cause trouble.

Describe a real-world example that illustrates the Interface Segregation Principle.

Consider everyday tools or devices with specialized controls.