University of Washington, CSE 142

Lab 10: Final Exam Practice

Except where otherwise noted, the contents of this document are Copyright 2013 Stuart Reges and Marty Stepp.

lab document created by Marty Stepp, Stuart Reges and Whitaker Brand

Basic lab instructions

• Mouse over highlighted words if you're not sure what they mean!
• Talk to your classmates for help.
• You may want to bring your textbook to future labs to look up syntax and examples.
• Stuck? Confused? Have a question? Ask a TA for help, or look at the book or past lecture slides.
• Complete as much of the lab as you can within the allotted time. You don't need to keep working on these exercises after you leave.
• Feel free to complete problems in any order.
• Make sure you've signed in on the sign-in sheet before you leave!

Today's lab

Goals for today:

• Practice problems in the same format as the final
• Find resources to help tackle exam problems
• Remember, the final is two hours. This lab is 50 minutes. Feel free to skip around!

You earn 1 point for each lab that you attend/show up on time for. Receiving credit for CSE 190 requires attending 8-10 labs. Please check that all your attendance records are correct on Canvas!

If you believe there is a problem with one of your scores, please email Fadel Shtiui at pludwig@cs.washington.edu.

Exam Tips

• Practice problems with pencil and paper. You will not be coding on a computer for the final. Many students find it extremely difficult to code on paper for the first time on exams.
• Do not put "" around output.
• If you're referring to the state of an array, use {}. If showing the printed output of an array, use the appropriate formatting (ex. if printed using Arrays.toString(), use [] around the array.)
• Review the cheat sheet. It is non-identical to the midterm one.
• No abbreviations/shorthand are allowed except S.o.p()/S.o.pln() for System.out.print() / System.out.println(), respectively.
• More information on the Exams tab of the course website! (soon!)

Reference mysteries

Reference mysteries test your understanding of reference semantics and value semantics. Review the difference in lab 8, slide 12!

Note: Remember that printing arrays using Arrays.toString() prints using [], not {}.

Exercise : reference mystery

    public static void main(String[] args) {
        int y = 1;
        int x = 3;
        int[] a = new int[4];
        mystery(a, y, x);                                             // 2 3 [0, 0, 17, 0]^0-9,+
        System.out.println(x + " " + y + " " + Arrays.toString(a));   // 3 1 [0, 0, 17, 0]^0-9,+
        x = y - 1;
        mystery(a, y, x);                                             // 1 0 [17, 0, 17, 0]^0-9,+
        System.out.println(x + " " + y + " " + Arrays.toString(a));   // 0 1 [17, 0, 17, 0]^0-9,+
    }
    public static void mystery(int[] a, int x, int y) {
        if (x < y) {
            x++;
            a[x] = 17;
        } else {
            a[y] = 17;
        }
        System.out.println(x + " " + y + " " + Arrays.toString(a));
    }

Exercise : Groceries

Write a method name groceries that accepts as its parameter a Scanner holding an input file. The data in the file represents grocery items purchased along with their price and their discount category. Your method should compute and return a real number representing the total cost of the grocery items.

Each item is represented by three tokens: (1) the name of the item (a single word), (2) its discount category ("red" (10% off full price), "blue" (25% off full price), or "none" (no discount)), and (3) its full price. The casing of the discount category is not guaranteed (for example, we could see "red", "RED", "rED", "rEd", or any other casing of the word "red").

avocado RED 1  blueberries none 5 milk blue 
   2.00       cream                   red 1.00    cereal None 1.29

If you finish them all...

If you finish all the exercises, try out our Practice-It web tool. It lets you solve Java problems from our Building Java Programs textbook.

You can view an exercise, type a solution, and submit it to see if you have solved it correctly.

Choose some problems from the book and try to solve them!