Q1:

Which three are valid method signatures in an interface?

1. private int getArea();
2. public float getVol(float x);
3. public void main(String [] args);
4. public static void main(String [] args);
5. boolean setFlag(Boolean [] test);

ANS:B - 2, 3 and 5

(2), (3), and (5). These are all valid interface method signatures. (1), is incorrect because an interface method must be public; if it is not explicitly declared public it will be made public implicitly. (4) is incorrect because interface methods cannot be static.