It's broken??

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Recommendation from mentor: "The University class there should have a getStudentWithLowestAverageGrade() without parameters, which returns a Student." Line 60 of the university class is exactly that???

6.1. Replace a parameter with a set of specialized methods. Replace the Student class's setValue() method
with specialized setCourse() and setAverageGrade() methods.
6.2. Add a parameter. Add a double parameter to the getStudentWithAverageGrade() method so the average grade of the required student is clear.
Implement the getStudentWithAverageGrade() method.
6.3. Remove a parameter. Remove the parameter from the getStudentWithHighestAverageGrade() method.
Implement this method. It should return the student with the highest average grade.
6.4. Separate a query from a modification. Split the getStudentWithLowestAverageGradeAndExpel() method into Student getStudentWithLowestAverageGrade() and void expel(Student student). The first method should return the student with the lowest average score, and the second method should expel the passed student (remove it from the students list).

Requirements:

Replace the Student class's setValue() method with specialized setCourse() and setAverageGrade() methods.
You need to add a double parameter to the University class's getStudentWithAverageGrade() method and implement the method.
You need to remove the parameter from the University class's getStudentWithHighestAverageGrade(double) method and implement the method.
You need to split the getStudentWithLowestAverageGradeAndExpel() method into Student getStudentWithLowestAverageGrade() and void expel(Student student), and implement these two methods.

package com.codegym.task.task29.task2909.car; import java.util.Date; public class Car { static public final int TRUCK = 0; static public final int SEDAN = 1; static public final int CABRIOLET = 2; double fuel; public double summerFuelConsumption; public double winterFuelConsumption; public double winterWarmingUp; private int type; private boolean driverAvailable; private int numberOfPassengers; public Car(int type, int numberOfPassengers) { this.type = type; this.numberOfPassengers = numberOfPassengers; } public int fill(double numberOfGallons) { if (numberOfGallons < 0) return -1; fuel += numberOfGallons; return 0; } public double getTripConsumption(Date date, int length, Date summerStart, Date summerEnd) { double consumption; if (date.before(summerStart) || date.after(summerEnd)) { consumption = length * winterFuelConsumption + winterWarmingUp; } else { consumption = length * summerFuelConsumption; } return consumption; } public int getNumberOfPassengersThatCanBeCarried() { if (!isDriverAvailable()) return 0; if (fuel <= 0) return 0; return numberOfPassengers; } public boolean isDriverAvailable() { return driverAvailable; } public void setDriverAvailable(boolean driverAvailable) { this.driverAvailable = driverAvailable; } public void startMoving() { if (numberOfPassengers > 0) { fastenPassengerBelts(); fastenDriverBelt(); } else { fastenDriverBelt(); } } public void fastenPassengerBelts() { } public void fastenDriverBelt() { } public int getMaxSpeed() { if (type == TRUCK) return 80; if (type == SEDAN) return 120; return 90; } }

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Henrique

Level 41 , São Paulo, Brazil

5 August 2020, 18:12

Can anyone explain this code to me, please?

public Student getStudentWithHighestAverageGrade() {
    Collections.sort(students, (o1, o2) -> {
        Double O1 = o1.getAverageGrade(), O2 = o2.getAverageGrade();
        return O1.compareTo(O2);
    });
    return students.get(students.size()-1);
}

public Student getStudentWithLowestAverageGrade() {
    Collections.sort(students, (o1, o2) -> {
        Double O1 = o1.getAverageGrade(), O2 = o2.getAverageGrade();
        return O1.compareTo(O2);
    });
    return students.get(0);
}

Guadalupe Gagnon

Level 37 , Tampa, United States

5 August 2020, 19:29

This is a lambda expression (added in Java 8 i believe) that replaces using a custom Comparator. Take for example this bit of code:

public static void main(String[] args) {
   ArrayList<Integer> temp = new ArrayList<>();
   temp.addAll(Arrays.asList(new Integer[] {3,5,2,7,4,6}));

   Collections.sort(temp, new Comparator<Integer>() {
      @Override
      public int compare(Integer o1, Integer o2) {
         return o1.compareTo(o2);
      }
   });

   Collections.sort(temp, (o1, o2) -> o1.compareTo(o2));

   System.out.println(temp);
}

lines 4-10 are exactly the same as line 12, the difference being that line 12 takes lines 4-10 and replaces the Comparator with a lambda expressions If you were to comment out only one and run the code, then comment only the other, they would run exactly the same

Henrique

Level 41 , São Paulo, Brazil

5 August 2020, 19:44

Hi, Guadalupe. Thanks. I'm gonna read your answer now, but first, can you help me on "Refactoring (part 8)"? It's an "easy" one, but I have NO IDEA what to do, and I'm stuck in it for hours, and I cannot advance on the course because of it... Thanks!

Henrique

Level 41 , São Paulo, Brazil

5 August 2020, 19:49

About the lambda expression, I think I understand most of it. So in the task example you replaced the part after "->" with an anonymous class, is that it? Thanks.

Guadalupe Gagnon

Level 37 , Tampa, United States

5 August 2020, 19:53

If you copied that into intelliJ, it would actually suggest to change the first one (the comparator) to a lambda expression. I actually don't implicitly use them when I code, but I go with intelliJ's suggestions to make the change.

Henrique

Level 41 , São Paulo, Brazil

5 August 2020, 19:59

When I was copying your code to pass this task I saw that IntelliJ suggested this. But I wouldn't know how to use it by my own haha. Thanks again, especially for the part 8!

Oleh

Level 32 , Kyiv, Ukraine

13 April 2019, 07:40

solution

getStudentWithMinAverageGrade

Guadalupe Gagnon

Level 37 , Tampa, United States

13 April 2019, 14:18

It worked!! Solved on my 47th attempt. How did you come up with that? No where (in English) does it say that Lowest should be Min. I appreciate all the help though.

Oleh

Level 32 , Kyiv, Ukraine

13 April 2019, 14:23

need to be ready for anything