CS 1713/1711 Introduction to Computer Science Lecture 30

CS 1713 Lecture 30: Classes Containing Arrays
November 8, 1999

Look at the VButton examples from last lecture in preparation for Laboratory 9.
Example: What information should be in an entry representing a student in a class list? Alternatives: store a reference to a student object or store a student ID and look it up later. What are the implications of these alternatives?
Example: Define an array of 50 objects of type EnrollmentEntry
```
    EnrollmentEntry [] classList = new EnrollmentEntry[50];
```
What does classList look like at this point?

Example: Write code to prompt the user to enter the student's names and fill the classList array.

    SimpleGUI wind = new SimpleGUI();
    for (int k = 0; k < classList.length; k++) {
        String name = getString("Enter student name");
        classList[k] = new EnrollmentEntry(name);
    }

Example: Enter a grade for the k-th student.
```
    classList[k].setGrade(newValue);
```

Example: Produce a class roster:

    for (int k = 0; k < classList.length; k++) {
        System.out.println(k + ":" + classList[k].getName());
    }

Example: Set the grade for a particular student:

     void int findName(EnrollmentEntry [] g, String name) {
        for (int k = 0; k < g.length; k++) {
           if (name.equals(g[k].getName()));
              return k;
        }
        return -1;
     }

The findName function assumes that all the entries are filled.

Example: Make a class called Course that has an EnrollmentEntry array as field. What methods should this class have. Observe how the findName function changes.
Example Compare methods for setting the grade of the k-th student with setting the grade for a student with a particular name.

Objective: Understand how arrays of objects can be manipulated.

Last revision: November 6, 1999 at 4:30 pm