CS241: Spring 2017 -- Lecture 2

1. Reading assignment (for Tues), Chapter 5
2. On beginnings (and endings)
3. Java and the process of programming
   • Make all your code simple; that way it is easy to debug! Debugging can be the most difficult, frustrating, and time consuming part of programming. :(
     Debugging techniques:
     1. Analysis
     2. souts - to see the values of variables as it runs
     3. the debugger - to stop, step your program, see (and change!!) values live
     4. More sophisticated (for use in a larger program): debugging switch(es)
     5. Bracket problem section with try{...}catch
   • Quick Java review
   • Test classes/methods *before* you use them in some larger context!!
   • How to test a class/method? (write public static void main(String [] foo) in it and use Run File).
   • Iterating over (and souting each element of) an array: the old and the new; advantages and disadvantages

     1.                     for (int i=0; i<list.length; i++) {
                                System.out.println("\t" + list[i]);
                            }
                                    

     2.                     for (int nextInt: list) {
                                System.out.println("\t" + nextInt);
                            }
                                    

     3. Testing them; pass them an array to display... how to initialize?
   • A Singleton class is one which is never instantiated, and all its methods are static
     Example: Utils, with methods boolean isPowerOf2(int), and int getMeAnInt(String>
4. Seeding: given n, a power of 2, generate (and return) an array with the initial pairings for a seeded tournament of size n: so your whole could be: display(generateSeeded(n));! Assuming void display(int[] seeds){...}, the signature must be int[] generateSeeded(int). Two ways to go at it:
   • Iteratively: start with array (called list) of length 2, containing 1 and 2; while (list.length < n) {use list to create a new seeded list twice as long; store it in list (i.e. list = expand(list);)}; return list;
   • Recursively: start with array (called list) of length 2, containing 1 and 2; if (n = 2) return it; else return expand(generateSeeded(n/2);
5. How to write/test int[] expand(int[])? Two ways: old for loop, new for loop...