dtz_calling/StudentService.java

package com.example.classroomattendance.service;

import com.example.classroomattendance.model.Student;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

@Service
public class StudentService {
    private List<Student> students = new ArrayList<>();
    private Random random = new Random();

    public void addStudents(List<Student> studentList) {
        students.addAll(studentList);
    }

    public Student pickRandomStudent() {
        if (students.isEmpty()) {
            return null;
        }

        // 计算所有学生的总权重
        double totalWeight = 0;
        for (Student student : students) {
            totalWeight += getWeight(student);
        }

        // 随机选择权重范围内的值
        double randomValue = random.nextDouble() * totalWeight;

        // 选取符合该随机值的学生
        for (Student student : students) {
            randomValue -= getWeight(student);
            if (randomValue <= 0) {
                return student;
            }
        }

        // 防止极端情况下返回最后一个学生
        return students.get(students.size() - 1);
    }

    // 获取学生的权重，积分越高权重越低
    private double getWeight(Student student) {
        return 1.0 / (student.getPoints() + 1.0); // 防止分母为0
    }

    public void updateStudentPoints(Long id, double points) {
        for (Student student : students) {
            if (student.getId().equals(id)) {
                student.setPoints(student.getPoints() + points);
                break;
            }
        }
    }

    public List<Student> getAllStudents() {
        return students;
    }
}