CSE 142

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Each week you will complete problem(s) to turn in at your section. These problems will earn you up to 2 out of your 3 section participation points for the week. The other point is awarded for being present in your section and participating in the discussion.

You will not be graded on whether you have a perfect solution, but on whether you have demonstrated effort. Therefore please show some work that demonstrates how you got the answer rather than just writing the answer by itself. We will be somewhat lenient about exactly how the work is shown.

Our intention is that these problems would take you up to 30 minutes each week. If you find yourself taking significantly more than this, you may stop your work and write that you worked for 30 minutes. If you have made significant progress, we will still give you credit for your work.

Section 8: Classes/Objects (Thu Aug 15)

Exercises: Solve the following problem on paper and bring your sheet of paper to your section on Thursday:

  1. Inheritance. Assume that the following classes have been defined: 
     public class George extends Sally {
      public void method2() {
          System.out.println("george 2");
      }
  }
  
  public class Fred {
      public void method1() {
          System.out.println("fred 1");
      }
  
      public void method2() {
          System.out.println("fred 2");
      }
  
      public String toString() {
          return "fred";
      }
  }
  
  public class Harold extends Sally {
      public String toString() {
          return "harold";
      }
  }

  public class Sally extends Fred {
      public void method1() {
          System.out.println("sally 1");
      }
  
      public String toString() {
          return "sally";
      }
  }
    Consider the following code fragment: 
      Fred[] elements = {new Sally(), new Fred(), new George(), new Harold()};
  for (int i = 0; i < elements.length; i++) {
      System.out.println(elements[i]);
      elements[i].method1();
      elements[i].method2();
      System.out.println();
  }
    What output is produced by this code? (write the output as a series of 3-line columns in order from left to right)

Section 7: Arrays (Thu August 8)

Exercises: Solve the following problem on paper and bring your sheet of paper to your section on Thursday:

  1. Array Simulation. You are to simulate the execution of a method that manipulates an array of integers. Consider the following method: 
        public static void mystery(int[] list) {
        for (int i = 1; i < list.length - 1; i++) {
            if (list[i] > list[i - 1]) {
                list[i + 1] = list[i - 1] + list[i + 1];
            }
        }
    }
    Below are a list of specific lists of integers. You are to indicate what values would be stored in the list after method mystery executes if the given integer list is passed as a parameter to mystery. 
        {2, 4}
    {1, 2, 3}
    {2, 2, 2, 2, 2}
    {1, 2, 2, 2, 2}
    {2, 4, 6, 8}
    Show your work by writing the array's initial contents and then crossing out elements and writing new values as they change.

Section 6: File Input/Output (Thu Aug 1)

Exercises: Solve the following problem on paper and bring your sheet of paper to your section on Thursday:

  1. Token Based Processing. Write a static method processData that takes as a parameter a Scanner holding a sequence of integers and that reports each of the cumulative sums of the sequence along with the average of the numbers. For example, if the Scanner contains the following data: 
            8 4 2 9 7 13 5 9
    your method should produce the following output: 
            Sum of 1 = 8
        Sum of 2 = 12
        Sum of 3 = 14
        Sum of 4 = 23
        Sum of 5 = 30
        Sum of 6 = 43
        Sum of 7 = 48
        Sum of 8 = 57
        Average = 7.125
    Notice that the various lines of output report the sum including just the first number, then including the first two numbers, then including the first three numbers, and so on, up to the sum including all numbers. The final line of output reports the average of the sequence of numbers. Notice that this is the average of the numbers themselves, not the average of the cumulative sums.

    The amount of output will vary depending upon how many numbers are in the sequence. For example, if the Scanner contains the following values: 

            1 2 3 4
    the method should produce the following output: 
            Sum of 1 = 1
        Sum of 2 = 3
        Sum of 3 = 6
        Sum of 4 = 10
        Average = 2.5
    You are to exactly reproduce the format of these sample outputs. You may assume that the Scanner has at least one integer to be processed.

Section 5: Midterm practice (Thu July 25)

Exercises: Solve the following problem on paper and bring your sheet of paper to your section on Thursday:

  1. Self-Check 5.4: while loop mystery (p369 3rd Edition, p359 2nd Edition). For each method call, make a table showing the values that x and y have as you execute the while loop for that particular call. For example, for the first two calls, the tables look like this:

        mystery(19);              mystery(42);

    x     y                   x     y
    --------                  --------
    19    0                   42    0
                              21    1
    You are to write out the tables for the other three cals. This problem is included in PracticeIt, but PracticeIt doesn't ask for the tables (just the final output). But you can still use PracticeIt to see this problem.
  2. Assertions. You will identify various assertions as being either always true, never true or sometimes true/sometimes false at various points in program execution. The comments in the method below indicate the points of interest. 
            public static int mystery(int x) {
            int y = 1;
            int z = 0;
            // Point A
            while (x > y) {
                // Point B
                z = z + x - y;
                x = x / 2;
                // Point C
                y = y * 2;
                // Point D
            }
            // Point E
            return z;
        }
    Copy the table below onto a sheet of paper and fill it in with the words ALWAYS, NEVER or SOMETIMES.

      x > y z > 0 y % 2 == 0
    Point A      
    Point B      
    Point C      
    Point D      
    Point E      

Section 4: if/else, Scanner, return (Thu July 18)

Exercises: Solve the following problems on paper and bring your sheet of paper to your section on Thursday:

  1. Programming Exercise 4.1: fractionSum (p296 2nd edition, p305 3rd edition). You can use PracticeIt to solve this problem.
  2. Programming Exercise 4.9 (2nd edition) / 4.12 (3rd edition): printTriangleType (p298 2nd edition, p307 3rd edition). You can use PracticeIt to solve this problem.

Section 3: parameters, graphics (Thu July 11)

Exercises: Solve the following two (2) problems on paper and bring your sheet of paper to your section on Thursday:

  1. Parameter Mystery, Consider the following program: 
      public class Params {
      public static void main(String[] args) {
          int x = 15;
          int y = 2;
          int z = 9;

          mystery(x, y, z);
          mystery(z, x, y);
          mystery(y, z, x);
          mystery(x - z, z, z);
      }

      public static void mystery(int x, int y, int z) {
          System.out.println("The " + x + " monkeys ate " + (y + z) + " bananas");
      }
  }
    Make a table that shows what value is being passed to each of x and y and z for each of the four calls and then indicate the output produced by the program.
  2. Programming Exercise 3G.1 Remember that you can use PracticeIt to solve this problem.

Section 2

Cancelled due to Independence Day. The 07/05 lecture will be spent going over what would have been the Section 2 materials, so for more practice, see the materials from the 07/05 lecture.