Why don't all Java classes have interfaces?

Question

I have this question for homework and I'm not sure how to answer it. could you help me?

Answer 1

For any question “why not ...”, it’s good to think about “what happens if ...”. In this case: what happens if an interface is needed for each Java class? How will this change existing APIs? How will this make a difference for people creating new classes? Any problems that arise when answering these other questions may be the answer to your original question.

Answer 2

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