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);

(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.