Java - 如何找到在 Student 类中编写方法的得分最高的学生？

Question

我是 Java 初学者，陷入了一项任务。如果有人能帮助我，我将非常感激。我有一个具有这些属性的学生类(class) - 姓名、化学分数、数学分数和物理分数。在主课中，我与几个学生创建了一个 ArrayList。我的任务是找到所有学生中化学分数最高、数学分数最高和物理分数最高的学生(他们的名字)。我在 Main 类的 main 方法中执行了此操作，但问题是我必须在 Student 类中编写此操作，但此时我无法执行此操作。

这是我的代码:

public class Student {

    protected String name;
    private int chemistry;
    private int mathematics;
    private int physics;


    public Student(String name, int chemistry, int mathematics, int physics) {
        this.name = name;
        this.chemistry = chemistry;
        this.mathematics = mathematics;
        this.physics = physics;
    }

    public int getChemistry() {
        return chemistry;
    }

    public void setChemistry(int chemistry) {
        this.chemistry = chemistry;
    }

    public int getMathematics() {
        return mathematics;
    }

    public void setMathematics(int mathematics) {
        this.mathematics = mathematics;
    }

    public int getPhysics() {
        return physics;
    }

    public void setPhysics(int physics) {
        this.physics = physics;
    }
}

import java.util.ArrayList;

public class Main {

    public static void main(String[] args) {


        Student tom = new Student("Tom", 7, 6, 4);
        Student rome = new Student("Rome", 9, 5, 8);
        Student jack = new Student("Jack", 6, 9, 8);
        Student simon = new Student("Simon", 10, 8, 5);
        Student darek = new Student("Darek", 10, 9, 8);

        ArrayList<Student> students = new ArrayList<>();

        students.add(tom);
        students.add(rome);
        students.add(jack);
        students.add(simon);
        students.add(darek);


        System.out.println("Student(s) with the highest Chemistry grade among all students:");

        int max = 0;
        String names = null;
        for (int i = 0; i < students.size(); i++) {
            if (max == students.get(i).getChemistry()) { 
                names += ", " + students.get(i).name;
            } else if (max < students.get(i).getChemistry()) {
                       max = students.get(i).getChemistry(); 
                       names = students.get(i).name; 
            }
        }
        System.out.println(names);


        System.out.println();
        System.out.println("Student(s) with the highest Mathematics grade among all students:");

        max = 0;
        names = null;
        for (int i = 0; i < students.size(); i++) {
            if (max == students.get(i).getMathematics()) {
                names += ", " + students.get(i).name;
            } else if (max < students.get(i).getMathematics()) {
                       max = students.get(i).getMathematics();
                       names = students.get(i).name; 
            }
        }
        System.out.println(names);


        System.out.println();
        System.out.println("Student(s) with the highest Physics grade among all students:");


        max = 0;
        names = null;
        for (int i = 0; i < students.size(); i++) {
            if (max == students.get(i).getPhysics()) {
                names += ", " + students.get(i).name;
            } else if (max < students.get(i).getPhysics()) {
                       max = students.get(i).getPhysics();
                       names = students.get(i).name; 
            }
        }
        System.out.println(names);

    }
}

我尝试在 Student 类中编写类似的方法:

public int bestOfChemistry(int max, String names) {
        if (max == chemistry) {
            names += ", " + name;   
        } else if (max < chemistry) {
            max = chemistry;
            names = name;
        }
        return max;
    }

但是当我尝试在主类中使用此方法时，我只能获得最高等级。我知道，因为我只在 bestOfChemistry(..) 方法中返回了它，但我也不知道如何获取它们的名字:

int max = 0;
String names = null;
for (int i = 0; i < students.size(); i++) {
            max = students.get(i).bestOfChemistry(max, names);
        }
        System.out.println(max);

我也不知道如何为这三个类(class)编写一个方法来避免多个相同的方法。

Answer 1

您不应该创建引用代表单个对象的类中的多个对象的方法，这在语义上没有意义。

编辑:由于您不允许在主类(class)中这样做，因此您可以添加一个新类(class)，其功能是寻找最好的学生。例如，我将其命名为“StudentsFinder”。它看起来像这样:

class StudentsFinder {

    private final ArrayList<Student> students;
    private ArrayList<String> bestStudents;

    StudentsFinder(ArrayList<Student> students) {
        this.students = students;
    }

    ArrayList<String> getBestChemistryStudents() {
        bestStudents = new ArrayList<>();
        int maxChemistryGrade = 0;
        //We look for the best grade first.
        for (Student student : students) {
            if (student.getChemistry() > maxChemistryGrade) {
                maxChemistryGrade = student.getChemistry();
            }
        }
        //Now we can add those students with the best grade in the array
        for (Student student : students) {
            if (student.getChemistry() == maxChemistryGrade) {
                bestStudents.add(student.getName());
            }
        }
        //And we return the results
        return bestStudents;
    }
    //The following methods do the same thing but with math and physics grades, respectively 
    ArrayList<String> getBestMathStudents() {
        bestStudents = new ArrayList<>();
        int maxMathGrade = 0;
        for (Student student : students) {
            if (student.getMathematics() > maxMathGrade) {
                maxMathGrade = student.getMathematics();
            }
        }
        for (Student student : students) {
            if (student.getMathematics() == maxMathGrade) {
                bestStudents.add(student.getName());
            }
        }
        return bestStudents;
    }

    ArrayList<String> getBestPhysicsStudents() {
        bestStudents = new ArrayList<>();
        int maxPhysicsGrade = 0;
        for (Student student : students) {
            if (student.getPhysics() > maxPhysicsGrade) {
                maxPhysicsGrade = student.getPhysics();
            }
        }
        for (Student student : students) {
            if (student.getPhysics() == maxPhysicsGrade) {
                bestStudents.add(student.getName());
            }
        }
        return bestStudents;
    }
}

在 Student 类中，您将需要一个名称的 setter/getter :

public String getName() {
    return name;
}

然后，您可以在主类中添加一个新的 StudentsFinder 实例，在构造函数中将 Students 数组传递给它，然后调用每个方法:

StudentsFinder finder = new StudentsFinder(students);

System.out.println("Student(s) with the highest Chemistry grade among all students:");
System.out.println(finder.getBestChemistryStudents());

System.out.println("Student(s) with the highest Mathematics grade among all students:");
System.out.println(finder.getBestMathStudents());

System.out.println("Student(s) with the highest Physics grade among all students:");
System.out.println(finder.getBestPhysicsStudents());

请注意，我们可以将结果直接传递给 println() 方法:

System.out.println(finder.getBestChemistryStudents());

...因为它自动调用ArrayList中的toString()，其实现继承自AbstractCollection类。它以 [value1, value2, ..., valueN] 格式打印所有值。