java - 返回 Hashset 中具有最高值的类对象

Question

我有 HashSet，其中包含对象列表，如学生、教授和系。它需要检查哪个学生得分最高，哪个教授的学生得分最高。示例代码表示类似

  class Student{
    public String Name;
    public int Age;
    public int TotalMarks;
}
class Professor{
    public String Name;
    public int Age;
    public Student Student_Assigned;
}

class Department{
    Set<Professor> collectionDept = new HashSet<Professor>();

    public Student getStudentWithHigestMarks(){
        return null;
    }
}

我如何使用 java 找到它？

Answer 1

实现 Comparable 并对您的 Collection 进行排序/操作。

例如在你的主代码中:

Student bad = new Student("bad");
bad.setMarks(2);
Student meh = new Student("meh");
meh.setMarks(5);
Student good = new Student("good");
good.setMarks(10);
Student otherGood = new Student("otherGood");
otherGood.setMarks(10);

// initializes a Set of students
Set<Student> students = new HashSet<Student>();
// adds the students
students.add(meh);
students.add(bad);
students.add(good);
students.add(otherGood);
// prints the "best student"
System.out.println(Collections.max(students).getName());
// initializing Set of best students
List<Student> bestStudents = new ArrayList<Student>();
// finding best mark
int bestMark = Collections.max(students).getMarks();
// adding to best students if has best mark
for (Student s: students) {
    if (s.getMarks() == bestMark) {
        bestStudents.add(s);
    }
}
// printing best students
for (Student s: bestStudents) {
    System.out.println(s.getName());
}

输出:

good
good
otherGood

...这是您的Student 类的草稿:

public class Student implements Comparable<Student> {
    // we use encapsulation and set the fields' access to private
    private String name;
    private int age;
    private int marks;
    // we use encapsulation and have setters/getters/constructor access for the private fields
    public Student(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public int getMarks() {
        return marks;
    }
    public void setMarks(int marks) {
        this.marks = marks;
    }
    // TODO other setters/getters
    // here we implement the compareTo method and decide which int to return according to the "marks" field
    @Override
    public int compareTo(Student otherStudent) {
        if (marks < otherStudent.getMarks()) {
            return -1;
        }
        else if (marks > otherStudent.getMarks()) {
            return 1;
        }
        else {
            return 0;
        }
    }

您可能还想仔细看看 documentation对于 Comparable 接口(interface)。