C++语言构建一个小型的班级学生健康管理系统，对于每个学生应该统计下述数据：学号、姓名、出生日期、性别、身高、体重、身体状况等信息，并根据班级平均体重来判断该同学体重水平。请抽象出该系统中的类及其之间的关联，分析归纳出类的相关属性和功能并进行代码设计。要求如下： （1）使用UML图表示类的属性方法及类之间的关系 （2）请使用静态成员对学生数量及体重总和进行定义 （3）定义函数显示该同学的体重水平，规则为体重在平均体重上下50%的为正常体重，体重低于平均体重的50%为较轻，体重高于平均体重的50%为较重。 （4）设计方法输出学生健康的统计信息

根据您的需求，我为您设计了一个小型班级学生健康管理系统的类和其之间的关联。以下是UML图和代码设计：

#include <iostream>
#include <vector>

class Student {
private:
    static int numStudents;
    static double totalWeight;
    int studentID;
    std::string name;
    std::string birthDate;
    char gender;
    double height;
    double weight;
    
public:
    Student(std::string name, std::string birthDate, char gender, double height, double weight) {
        this->studentID = numStudents++;
        this->name = name;
        this->birthDate = birthDate;
        this->gender = gender;
        this->height = height;
        this->weight = weight;
        totalWeight += weight;
    }
    
    static int getNumStudents() {
        return numStudents;
    }
    
    static double getAverageWeight() {
        return totalWeight / numStudents;
    }
    
    void displayWeightStatus() {
        double averageWeight = getAverageWeight();
        double weightPercentDiff = ((weight - averageWeight) / averageWeight) * 100;
        
        if (weightPercentDiff >= -50 && weightPercentDiff <= 50) {
            std::cout << name << "'s weight is normal." << std::endl;
        } else if (weightPercentDiff < -50) {
            std::cout << name << "'s weight is lighter than average." << std::endl;
        } else {
            std::cout << name << "'s weight is heavier than average." << std::endl;
        }
    }
    
    static void displayHealthStatistics() {
        std::cout << "Total number of students: " << numStudents << std::endl;
        std::cout << "Average weight: " << getAverageWeight() << std::endl;
    }
};

int Student::numStudents = 0;
double Student::totalWeight = 0.0;

int main() {
    std::vector<Student> students;
    
    // 添加学生
    students.push_back(Student("Tom", "1999-01-01", 'M', 170.0, 65.0));
    students.push_back(Student("Alice", "2000-02-02", 'F', 160.0, 50.0));
    students.push_back(Student("Bob", "1998-03-03", 'M', 180.0, 80.0));
    
    // 显示学生体重水平
    for (const auto& student : students) {
        student.displayWeightStatus();
    }
    
    // 显示学生健康统计信息
    Student::displayHealthStatistics();
    
    return 0;
}

UML图如下：

+--------------------------------+
|           Student              |
+--------------------------------+
| - numStudents: int (static)    |
| - totalWeight: double (static) |
| - studentID: int               |
| - name: string                 |
| - birthDate: string            |
| - gender: char                 |
| - height: double               |
| - weight: double               |
+--------------------------------+
| + Student(name: string,        |
|            birthDate: string,   |
|            gender: char,        |
|            height: double,      |
|            weight: double)      |
| + getNumStudents(): int (static)|
| + getAverageWeight(): double    |
|   (static)                     |
| + displayWeightStatus(): void   |
| + displayHealthStatistics(): void|
+--------------------------------+
| + main(): int                  |
+--------------------------------+

以上代码定义了一个名为`Student`的类，具有学生的相关属性和功能。其中，`numStudents`和`totalWeight`是静态成员变量，用于统计学生数量和体重总和。构造函数用于初始化学生对象的属性，并更新静态成员变量的值。`getNumStudents()`和`getAverageWeight()`是静态成员函数，用于获取学生数量和平均体重。`displayWeightStatus()`方法根据平均体重判断学生的体重水平，并进行相应输出。`displayHealthStatistics()`方法用于显示学生健康的统计信息。在`main()`函数中，我们创建了几个学生对象，并进行了相应的操作和输出。

希望这个设计满足了您的需求。如果有任何问题，请随时向我提问！