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Discussion :: Declarations and Access Control

  1. interface DoMath  {     double getArea(int rad);  } interface MathPlus  {     double getVol(int b, int h);  } /* Missing Statements ? */
    which two code fragments inserted at end of the program, will allow to compile?
    1. class AllMath extends DoMath { double getArea(int r); }
    2. interface AllMath implements MathPlus { double getVol(int x, int y); }
    3. interface AllMath extends DoMath { float getAvg(int h, int l); }
    4. class AllMath implements MathPlus { double getArea(int rad); }
    5. abstract class AllMath implements DoMath, MathPlus { public double getArea(int rad) { return rad * rad * 3.14; } }

    2. A.
    1 only
    B.
    2 only
    C.
    3 and 5
    D.
    1 and 4

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    Answer : Option C

    Explanation :

    (3) are (5) are correct because interfaces and abstract classes do not need to fully implement the interfaces they extend or implement (respectively).

    (1) is incorrect because a class cannot extend an interface. (2) is incorrect because an interface cannot implement anything. (4) is incorrect because the method being implemented is from the wrong interface.

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