CIS2168
TEN MINUTE TEST #1
September 7, 2010




(5)	1. Assume that the class B extends the class A (A is abstract, 
	B is concrete). Show which assignments are legal/not and why
	   B b = new B();
	   A a = new A();
	   A c = b;
	   B d = c;








(10)	2. Why do we use Abstract classes, like Number, from Java API, or Shape
	as described in class?











(5)     3. What is wrong with this code? explain.
		public class Temp {
		    static int x;
		    int y;
		    public static void main(String[] args) {
			System.out.println(x);
			System.out.println(y);
		    }
		}






(15)	4. Implement the method public static double avg(int[][] a)
	that returns the average of the values stored in a. You can
	assume than nothing in a is null.