Why does Java forbid multiple inheritance of classes?
PICTURE THIS: OOP PILLARS
Simple meaning
If two parents define the same method, the compiler would not know which one to pick, the diamond problem.
WHY — OOP instead of guessing?
Why interviewers care about OOP:
on OOP.
the situation, the default choice, and one exception - that reads as experience.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1If two parents define
the same method, the compiler would not know which one to pick, the diamond problem.
- 2Interfaces avoid that by
allowing multiple contracts with default-method conflict rules.
- 3You still get reuse
through composition and interface implementation.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
If two parents define the same method, the compiler would not know which one to pick, the diamond problem. Interfaces avoid that by allowing multiple contracts with default-method conflict rules.