CIS1068
                              MIDTERM 2 


(5)   1. What are you trying to do in Testing? 







(5)   2. What is a stub? How does it help us?






(10)  3. (1) A data member of a class is said to be private.
	     What does it mean?
	 (2) A data member of a class is said to be an instance data member.
	     What does it mean?











(10)  5. If we execute
                double x = scan.nextDouble();
         where scan is a Scanner, we may run into an exception if the user enters something
         like "a23.8". Use the try .. catch statement to deal with this problem.












(5)   5. What is the signature of a method? Give an example








(10)  6. Here are some assignments. Indicate if they are correct
	 and, if wrong, correct them (don't change the type of variables):
	(a)	int x = 3.4;
	(b)	Integer v = 12;
	(c)	double z = 3;
	(d)	float w = z;
	(e)	int u = 'x';
	(f) 	char c = u;




(15)  7. Define a class with a constant, a static data member, an 
	 instance data member, a constructor, an instance method with 
	 a formal parameter and a local variable.


















(10)  8. What is the value of the expression below
         (show all the steps used in evaluating this
         expression):
	   (5 > 4 + 3 * 2/3) || ( 3 % 2 != 3) && 1 < 3















(5)   9. What is printed out by the fragment
                int a = 1;
                foo(a);
		System.out.println("a = " + a);
	 where foo is defined as
                public static void foo(int a) {
                   a = a + 3;
		   System.out.println("a = " + a);
                }
	 Explain.






(10) 10. Given the following method moo: 
            static String moo(String s1, char c, String s2) {
	       String who = "";
	       for (int k = 0; k < s1.length(); k++) {
		   char d = s1.charAt(k);
		   if (c == d)
			who += s2;
		   else
			who += d;
	       }
               return who;
            }
         Show what is returned by the call moo("abracadabra", 'b', "bra");
         and more in general what is the purpose of this method.










(5)  11. What is the output of
	int k = 3;
	while (k > 1) {
	    int r = k % 2;
	    switch (r) {
	    case 0:  k = k/2;
		     break;
	    case 1:  k = 3*k+1;
	    }
	    System.out.print(k + " ");
	}






(10) 12. After the statement "int[][] m = {{1,2},{3,4,5,6}}; is executed
	 specify the value of each of the following expressions:
	  m[1] =
	  m.length =
	  m[1][m[1].length-1] =
	  m[2][2] =
	  m[0].length + m[1].length = 




(10) 13. Assuming
	    public static void foo(int[] a) {
		for (int k = 0; k < a.length; k++)
		    a[k] += 2;
	    }
	  What will be the content of the array int[] b = {1,2,3};
	  after the call foo(b)?
	






(15) 14. Write a static method isPrime that, applied to a positive 
	 integer n returns true if and only if n is a prime.

















(15) 15. Write a static method avg that returns the average value
         of a two dimensional array of integers. You may assume no 
	 array is null or empty.
	 
















(15) 16. Remember the Fraction class. Add to it the method
            public int compareTo(Fraction a);
         which returns -1, 0, +1  if the subject of the method, i.e. the "this"
         object, is less, equal, or greater than a.















(20) 17. Complete all methods below for the class IntArray
	public class IntArray {
	    private int[] a;

	    // constructor with given length for a
	    public IntArray(int length) {
		
	    }

	    // accessor returning the length of a
	    public int length() {

	    }

	    // accessor, return the element at position j in a
	    public int elementAt(int j) {

	    }

	    // modifier/setter, set element at position j in a to v
	    public void setElementAt(int j, int v) {

	    }

	    // Equal test, returns true if 2 IntArrays are same reference
	    public boolean identical(IntArray b) {


	    }

	    // Equivalence test, returns true if 2 arrays have samecontent
	    public boolean equals(IntArray b) {



	    }
         }

(10) 18. Suppose you have to write the linearSearch method to find an 
	 integer who in the integer array a. You will need to write a
	 loop. Write the loop invariant of this loop without writing the 
	 loop itself.









(5)  19. Given an array with content {5,3,2,6,1} show its content 
	 at the end of the first pass in the selection sort algorithm










(10) 20. Write a method foo with no parameters that returns an ArrayList of Fraction
	 containing two fractions with value respectively, 2/3 and 3/5.