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16.6. StudentAnswerSheet - Part B

Part b. Consider the following class that represents the test results of a group of students that took a multiple-choice test.

public class TestResults
{
   private List<StudentAnswerSheet> sheets;

   /** Precondition: sheets.size() > 0;
    *                all answer sheets in sheets have the same number of answers
    *  @param key the list of correct answers represented as strings of length one
    *         Precondition: key.size() is equal to the number of answers in each
    *                       of the answer sheets in sheets
    *  @return the name of the student with the highest score
    */
  public String highestScoringStudent(List<String> key)
  {
    /* to be implemented in part (b) */
  }

  // There may be fields, constructors, and methods that are not shown.
}

Write the TestResults method highestScoringStudent, which returns the name of the student who received the highest score on the test represented by the parameter key. If there is more than one student with the highest score, the name of any one of these highest-scoring students may be returned. You may assume that the size of each answer sheet represented in sheets is equal to the size of key.

16.6.1. Try and Solve It

Complete method highestScoringStudent below.

The code below has a main method for testing the highestScoringStudent method.

import java.util.ArrayList; import java.util.List; import java.util.Arrays; class StudentAnswerSheet { private List<String> answers; // the list of the student's answers private String name; public StudentAnswerSheet(String nm, List<String> ans) { name = nm; answers = new ArrayList<String>(); for (String a : ans) answers.add(a); } /** @param key the list of correct answers, represented as strings of length one * Precondition: key.size() is equal to the number of answers in this answer sheet * @return this student's test score */ public double getScore(ArrayList<String> key) { double score = 0; for (int i = 0; i < key.size(); i++) { if (key.get(i).equals(answers.get(i))) score = score + 1.0; else if (!answers.get(i).equals("?")) score = score - 0.25; } return score; } /** @return the name of the student */ public String getName() { return name; } } public class TestResults { private ArrayList<StudentAnswerSheet> sheets; public TestResults(ArrayList<StudentAnswerSheet> shs) { sheets = new ArrayList<StudentAnswerSheet>(); for (StudentAnswerSheet s : shs) sheets.add(s); } /** Precondition: sheets.size() > 0; * all answer sheets in sheets have the same number of answers * @param key the list of correct answers represented as strings of length one * Precondition: key.size() is equal to the number of answers * in each of the answer sheets in sheets * @return the name of the student with the highest score */ public String highestScoringStudent(ArrayList<String> key) { //*** Write this method! *** } public static void main(String[] args) { ArrayList<String> key = new ArrayList<String>(Arrays.asList( new String[] {"A", "C", "D", "E", "B", "C", "E", "B", "B", "C"})); ArrayList<String> answers1 = new ArrayList<String>(Arrays.asList( new String[] {"A", "B", "D", "E", "A", "C", "?", "B", "D", "C"})); StudentAnswerSheet s1 = new StudentAnswerSheet("S1", answers1); System.out.println("Your score for s1 is: " + s1.getScore(key) + " and should be 5.25"); ArrayList<String> answers2 = new ArrayList<String>(Arrays.asList( new String[] {"A", "?", "D", "E", "A", "C", "?", "B", "D", "C"})); StudentAnswerSheet s2 = new StudentAnswerSheet("S2", answers2); System.out.println("Your score for s2 is: " + s2.getScore(key) + " and should be 5.5"); ArrayList<String> answers3 = new ArrayList<String>(Arrays.asList( new String[] {"A", "?", "D", "E", "A", "C", "E", "B", "D", "C"})); StudentAnswerSheet s3 = new StudentAnswerSheet("S3", answers3); System.out.println("Your score for s3 is: " + s3.getScore(key) + " and should be 6.5"); ArrayList<String> answers4 = new ArrayList<String>(Arrays.asList( new String[] {"A", "C", "D", "E", "A", "C", "E", "B", "D", "C"})); StudentAnswerSheet s4 = new StudentAnswerSheet("S4", answers4); System.out.println("Your score for s4 is: " + s4.getScore(key) + " and should be 7.5"); ArrayList<StudentAnswerSheet> sheets = new ArrayList<StudentAnswerSheet>(); sheets.add(s1); sheets.add(s2); sheets.add(s3); sheets.add(s4); TestResults results = new TestResults(sheets); System.out.println("Your best is: " + results.highestScoringStudent(key) + " and should be S4"); } }

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