Multiple choice technology web technology

Which is true? (Choose all that apply.)

  1. "X extends Y" is correct if and only if X is a class and Y is an interface

  2. "X extends Y" is correct if and only if X is an interface and Y is a class

  3. "X extends Y" is correct if X and Y are either both classes or both interfaces

  4. "X extends Y" is correct for all combinations of X and Y being classes and/or interfaces
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Java, 'extends' is valid only when both X and Y are classes, or when both X and Y are interfaces. A class cannot extend an interface (it implements it), and an interface cannot extend a class. This rule maintains the type system's consistency - inheritance relationships must be between the same kind of type.

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