CSE 142: Computer Programming I, Spring 2011

Section 9: Final practice (Thu Jun 2)

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? (you may write the output as a series of 3-line columns in order from left to right)

Section 8: Classes and Objects (Thu May 26)

1. Critters. Define a Critter class called Ant. It should always infect if an enemy is in front of it. Otherwise it should randomly choose between the three other actions (HOP, LEFT, RIGHT). Each choice should be equally likely. Its color should be blue and its string should be "A". To work on this problem, you should download and unzip the Homework 8 files.

Section 7: Arrays (Thu May 19)

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 May 12)

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 5.5: Midterm practice (Thu May 5)

1. 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 += x - y;
   		x /= 2;
   		// Point C
   		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 5: while, Random, boolean (Thu Apr 28)

1. Self-Check 5.4: while loop mystery (p359). 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 Practice-It, but Practice-It doesn't ask for the tables (just the final output). But you can still use Practice-It to see this problem.
2. Programming Exercise 5.4 (p369). You can use Practice-It to solve this problem.

Section 4: if/else, Scanner, return (Thu Apr 21)

1. Programming Exercise 4.1: fractionSum (p296). You can use Practice-It to solve this problem.
2. Programming Exercise 4.9 printTriangleType (p298). You can use Practice-It to solve this problem.

Section 3: parameters, graphics (Thu Apr 14)

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 (p217). Remember that you can use Practice-It to solve this problem.

Section 2: expressions, for loops (Thu Apr 7)

1. from Self-Check 2.2 (p117), solve the following expressions (see note below):

   	14 / 7 * 2 + 30 / 5 + 1
   	(12 + 3) / 4 * 2
   	813 % 100 / 3 + 2.4
         

2. from Self-Check 2.3 (p118), solve the following expressions (see note below):

   	4.0 / 2 * 9 / 2
   	2.5 * 2 + 8 / 5.0 + 10 / 3
         

3. Programming Exercise 2.6 (p125). Remember that you can use Practice-It to solve this problem. If you do use Practice-It, don't forget to copy your solution to the paper submission.

For the expression problems, show how the expression is evaluated step-by-step, as is done on page 62 of the textbook. You should have a different line for each different operator that needs to be evaluated. Below is an example of what we expect:

      2 + 19 % 5 - (11 * (5 / 2))

      2 + 19 % 5 - (11 *    2   )

      2 +   4    - (11 *    2   )

      2 +   4    -       22

         6       -       22

                 -16
      

Section 1: basic Java, static methods (Thu Mar 31)

No problems are due for the first week's section.