Impact of Program Design

Vocabulary

English	Meaning
modular/ˈmɒdjʊlə/	modular

Two neat designs can report different averages

A fictional record contains scores 80, absent and 100. Treating absence as zero gives (80 + 0 + 100) / 3 = 60; omitting the absent result gives (80 + 100) / 2 = 90.
Separate methods can calculate either result correctly. Organization does not choose the reporting policy: establish what absence means, who decides, and which denominator the report must show before using the result.

A grading system needs more than neat method names

The same records give 60 or 90 under two explicit missing-score policies

Practice

Scores are 80, absent and 100. Under the available-score policy, what is the average?

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Turn a requirement into a contract

Specify whether absence means an unattempted assessed task, a task not assigned, or data not yet entered. These cases need not share a rule; the fictional example demonstrates consequences and does not prescribe a school grading policy.
State the accepted input, the treatment of missing values and the result. If the rule is “average available scores”, an all-missing record has no average; report that case explicitly instead of inventing zero or dividing by zero.

Separate responsibilities for checking

A modular 模块化 design separates readScores, averageAvailable and printReport. The average method can be checked with known values without reading a file or capturing formatted output.
Separation helps when interfaces remain clear. A change to the meaning of absence can still require changes in calculation, reporting and checks; small methods and good names alone do not prevent those dependencies.

Check ordinary and boundary cases

For the available-score policy, check [80, absent, 100] gives 90, a single 80 gives 80, and [absent, absent] produces the agreed “no result” outcome. Do not merely check that the program runs.
The calculation below uses null for missing values. It returns a double average and rejects the all-missing case. It assumes a non-null array of ordinary scores; input validation and reporting are separate responsibilities.

Example

public class AverageAvailable {
    public static double averageAvailable(Integer[] scores) {
        double total = 0;
        int present = 0;
        for (Integer score : scores) {
            if (score != null) {
                total += score;
                present++;
            }
        }
        if (present == 0) {
            throw new IllegalArgumentException("No available scores");
        }
        return total / present;
    }
}

Practice

A modular design (independent, well-named pieces) is mainly easier to...