Question 4-3

Define a class PassCount to track whether all the students of a class have passed a test. It should support the following methods.

PassCount(): (Constructor method) Constructs an object representing an empty class.
void addGrade(double grade): Adds grade into the class.
boolean isAnyFailing(): Returns true only if there is somebody in the class who received a grade of less than 60.

For example, if you defined this class properly, I should be able to write the following class to test it.

public class PassCountTest {
    public static void run() {
        PassCount a = new PassCount();
        a.addGrade(45.0);
        a.addGrade(76.0);
        IO.println(a.isAnyFailing()); // should print ``true''

        PassCount b = new PassCount();
        b.addGrade(60.0);
        IO.println(b.isAnyFailing()); // should print ``false''
    }
}

Note that, to accomplish this, a PassCount object need not remember every single grade --- that is, you do not need to use arrays: It just needs to remember whether any of the ones it has seen were below 60.

Solution

public class PassCount {
    private boolean found_fail;

    public PassCount() {
        found_fail = false;
    }

    public void addGrade(double grade) {
        if(grade < 60.0) {
            found_fail = true;
        }
    }

    public boolean isAnyFailing() {
        return found_fail;
    }
}

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