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CSE 331: Software Design & Implementation

CSE 331 Homework 1: Procedural Abstraction

Due Wednesday, July 1 at 11:59pm.

Task 1: Specification–implementation matching

We will consider several variants of the following method specification:

/**
 * "Clamps" the values of an array towards a certain value range.
 *
 * @param a the array to adjust; must be non-null
 * @param lo the low end of the target range
 * @param hi the high end of the target range
 * @requires lo <= hi
 * @modifies a
 * ... @effects given below ...
 */
public static void clamp(int[] a, int lo, int hi)

The five variants differ in their @effects as follows:

Spec A
  @effects sets every element less than lo to lo, every element greater than hi
           to hi, and every element already between lo and hi (inclusive) is
           left unchanged

Spec B
  @effects after the call, every element of a satisfies lo <= a[i] <= hi

Spec C
  @effects after the call, every element of a satisfies a[i] <= hi, and every
           element that was already between lo and hi (inclusive) is left
           unchanged

Spec D
  @effects after the call, every element of a satisfies a[i] <= hi

Spec E
  @effects after the call, every element of a satisfies a[i] >= lo

And now consider the following 4 implementations:

// Implementation 1
for (int i = 0; i < a.length; i++) {
    if (a[i] < lo) a[i] = lo;
    else if (a[i] > hi) a[i] = hi;
}

// Implementation 2
for (int i = 0; i < a.length; i++) {
    if (a[i] > hi) a[i] = hi;
}

// Implementation 3
for (int i = 0; i < a.length; i++) {
    if (a[i] < lo) a[i] = lo;
}

// Implementation 4
for (int i = 0; i < a.length; i++) {
    a[i] = hi;
}

For each implementation, say which specifications it satisfies.

Please format your answer as a list like this:

  • Impl 1: A, B, C
  • Impl 2: C, D, E
  • and so forth

(Note that those are not the actual answers.) Or, if you prefer, you can draw a table like we did in section.

Task 2: Specification strength

Compare the five specifications from Task 1. For each pair, fill in the cell in the table below by writing S if the spec on the left (the row) is stronger than the spec on top (the column), W if the row spec is weaker, and --- if the two are incomparable. The diagonal is marked X. Feel free to only fill out the entries above the diagonal, since the others are symmetric.

A B C D E
A X
B X
C X
D X
E X

Getting the starter code

Get the starter code via gitlab. Click the blue "Code" button in the top right, and the click Download directory as zip at the very bottom of the popup. Extract the resulting file on your machine. You should see the following files:

  • Histogram.java: Code you need to read, understand, and document for Task 3.
  • Csv.java: Provided helper library for reading CSV files.
  • Gradebook.java: Starter code for Task 4.
  • assignments.csv, categories.csv, grades.csv: Sample data for Task 4.

Software setup

You may use any Java development environment you want. If you have one you are already comfortable with, we recommend you use it.

Visual Studio Code and the Terminal

If you are looking for a Java development environment, we recommend Visual Studio Code because it is easy to set up. You will need the "Extension Pack for Java". (Open the extensions panel in VS Code and search for "Extension Pack for Java" and install it.)

Once you have VS Code and the extension pack installed, then:

  1. Use File -> Open Folder... and select the unzipped hw01 folder you downloaded earlier.
  2. Open the Histogram.java file.
  3. Use View -> Terminal and run the following commands:
javac Histogram.java

The code should compile without errors. Then run the program like this:

java Histogram --column 2 grades.csv

You should see this output:

Histogram of "quiz2"  (6 values, 10 bins)
 [ 60.00,  63.70):   1  ****************************************
 [ 63.70,  67.40):   1  ****************************************
 [ 67.40,  71.10):   0  
 [ 71.10,  74.80):   0  
 [ 74.80,  78.50):   0  
 [ 78.50,  82.20):   1  ****************************************
 [ 82.20,  85.90):   0  
 [ 85.90,  89.60):   1  ****************************************
 [ 89.60,  93.30):   1  ****************************************
 [ 93.30,  97.00]:   1  ****************************************

Task 3: Run and Document Histogram.java

Write a user manual for Histogram aimed at someone who is comfortable using the command line, but who is not a Java programmer.

You will need to read the code and probably try it out on some more examples to figure out what it does.

Write your user manual as a comment right above the line public class Histogram.

Task 4: Complete the implementation of Gradebook.java according to its specification.

The starter code contains a partial implementation of a gradebook terminal application that reads in grade data and computes student course grades.

Start by reading the user manual at the top of the Gradebook.java file.

There are four unimplemented methods in this file:

  • indexOfMin
  • dropLowest
  • computeCourseGrades
  • main

You are responsible for implementing dropLowest() and main(). You are not required to implement computeCourseGrades or indexOfMin

You must follow these additional rules:

  • Your implementation of dropLowest must use indexOfMin to figure out which scores to drop.
  • Your implementation of main must use computeCourseGrades to compute the course grades.
  • When grading your code, we will plug in our own implementations of indexOfMin and computeCourseGrades, so your code must be correct assuming any correct implementation of these methods.
  • Remember that users make mistakes, and they should not see exception stack traces even if they make mistakes.

In order to actually run your code, you may find it necessary to implement a version of indexOfMin and computeCourseGrades, but they will not be graded, and you do not need to turn them in. We will also provide an autograder environment on Gradescope where you can run your code and get some limited feedback.

AI Policy

You should not use any AI assistance for any part of this assignment.

Submission

Submit your solutions to tasks 1 and 2 to the "Homework 1 Written" assignment on Gradescope. Submit your solutions to tasks 3 and 4 to the "Homework 1 Coding" assignment on Gradescope.