Exam Solutions:
===============

1a)

Use .equals() when comparing two *objects* for equality.  Use == to
compare primitive types (e.g. int), or to check whether two object
references point to the same object in memory.

1b)

Declare a variable as local if it's only used in a single method.
This will reduce the complexity of your code, and eliminate bugs
that might arise from unrelated pieces of code accidentally changing
an instance variable.

1c)

In a count-controlled loop we know exactly how many times we want to
repeat some operation, and we can use a counter variable to keep track
of where we are in the process and when to stop.  An event-controlled
loop is one where we don't know how many iterations it will take, but
we know when we're done. (E.g. we keep guessing at combinations until
we find the right one.)


2a)

The method takes two Die instances and rolls them until the difference
in the sum of d1's rolls and the sum of d2's rolls is 10 or greater.
It returns the number of rolls required until that difference is
achieved.

2b)

If the two Die instances have different numbers of sides we would expect
the loop to run fewer times in general, since the difference should grow 
more quickly in that case.


3)

    public int sumRandomlySelectedValues (int[] nums, int n) {
        Random rng = new Random();
        int sum = 0;
        for(int i=0; i<n; i++) {
            int index = rng.nextInt(nums.length);
            sum = sum + nums[index];
        }
        return sum;
    }
    
    
4)
    
    public ArrayList<String> getNotesContaining(String txt) {
        ArrayList<String> list = new ArrayList<String>();
        for(String s : notes) {
            if (s.contains(txt)) {
                list.add(s);
            }
        }
        return list;
    }