关于java出生年月求年龄

java知道学生的学号，姓名，年龄，性别出生年月去求年龄和男生女生人数，为什么结果不对啊

代码发在下面

把你代码放出来啊，不然怎么知道问题

 
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
 
public class Student {
    String stuNum;
    String name;
    String sex;
//    Date birthDate;
    String birthYearMonth;
//    2000-01
 
    public  static  final String  MALE="男";
    public  static  final String  FEMALE="女";
 
    //格式：年-月
    public static final String fmtYm = "yyyy-MM";
 
    /**
     * 把符合日期格式的字符串转换为日期类型
     */
    public static Date stringtoDate(String dateStr, String format) {
        Date d = null;
        SimpleDateFormat formater = new SimpleDateFormat(format);
        try {
            formater.setLenient(false);
            d = formater.parse(dateStr);
        } catch (Exception e) {
            // log.error(e);
            d = null;
        }
        return d;
    }
 
    /**
     * 返回日期的年
     */
    public static int getYear(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        return calendar.get(Calendar.YEAR);
    }
 
//    https://blog.csdn.net/kiss_the_sun/article/details/6831051
     public  int getAge(){
//        Date date = DateUtil.stringtoDate(birthYearMonth, DateUtil.MONTG_DATE_FORMAT);
        Date date = stringtoDate(birthYearMonth,fmtYm);
        Date now = new Date();
//        Date.
        int yearNow = getYear(now);
        int yearBirth = getYear(date);
        return  yearNow-yearBirth;
 
//        return     DateUtil.dayDiff(now,date);
//        return  now-date;
//        Date date=new Date(Long.parseLong(time));
//        SimpleDateFormat formatter=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//        time=formatter.format(date);
 
//————————————————
//        版权声明：本文为CSDN博主「kiss_the_sun」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
//        原文链接：https://blog.csdn.net/kiss_the_sun/article/details/6831051
    }
}
 

import java.util.List;
 
public class StuClass {
    String clsNum;
    String name;
//    Student
    List<Student> students;
 
    public double avgAge(){
        double avg=0;
        for (Student student : students) {
            avg+=student.getAge();
        }
        return avg/students.size();
    }
 
    public  int cntOfMale(){
        int cnt=0;
        for (Student student : students) {
//            if(student.sex.equals("男人")){
//            if("男".equals(student.sex)){
            if(Student.MALE.equals(student.sex)){
                cnt++;
            }
        }
        return cnt;
    }
 
    public  int cntOfFemale(){
        int cnt=0;
        for (Student student : students) {
//            if(student.sex.equals("男人")){
//            if("女".equals(student.sex)){
            if(Student.FEMALE.equals(student.sex)){
                cnt++;
            }
        }
        return cnt;
    }
}
 
 

import java.util.List;
 
public class School {
    List<StuClass> stuClasses;
    public double avgClassStuCnt(){
        double cntAll=0;
        for (StuClass stuClass : stuClasses) {
            cntAll+=stuClass.students.size();
        }
        return  cntAll/stuClasses.size();
    }
}
 
 

import java.util.ArrayList;
 
public class Cal {
 
    static void calSchool() {
        School school = new School();
        school.stuClasses = new ArrayList<>();
        for (int i = 0; i < 3; i++) {
            school.stuClasses.add(mockClass(i));
        }
        double avgClassStuCnt = school.avgClassStuCnt();
        System.out.println("avgClassStuCnt");
        System.out.println(avgClassStuCnt);
    }
 
    static StuClass mockClass(int classNum) {
        StuClass stuClass = new StuClass();
 
 
//        stuClass.clsNum="20190911";
//        stuClass.name="信管191";
        stuClass.clsNum = "2019091" + classNum;
        stuClass.name = "信管19" + classNum;
        stuClass.students = new ArrayList<>();
//        for (int i = 0; i <3 ; i++) {
        for (int i = 0; i < 6; i++) {
            Student student = new Student();
            student.stuNum = "2019090" + i;
            student.name = "好人" + i;
//            student.sex="男人";
            student.sex = Student.MALE;
//            student.birthDate=new Date();
            student.birthYearMonth = "2000-0" + (i + 1);
            stuClass.students.add(student);
        }
        return stuClass;
    }
 
    static void testOneClass() {
        StuClass stuClass = new StuClass();
 
 
        stuClass.clsNum = "20190911";
        stuClass.name = "信管191";
        stuClass.students = new ArrayList<>();
//        for (int i = 0; i <3 ; i++) {
        for (int i = 0; i < 6; i++) {
            Student student = new Student();
            student.stuNum = "2019090" + i;
            student.name = "好人" + i;
//            student.sex="男人";
            student.sex = Student.MALE;
//            student.birthDate=new Date();
            student.birthYearMonth = "2000-0" + (i + 1);
            stuClass.students.add(student);
        }
 
        double avgAge = stuClass.avgAge();
        System.out.println("avgAge of class : " + stuClass.name);
        System.out.println(avgAge);
//        平均年龄
//        stuClass.
 
        int cntOfFemale = stuClass.cntOfFemale();
        int cntOfMale = stuClass.cntOfMale();
        System.out.println("cntOfFemale");
        System.out.println(cntOfFemale);
 
        System.out.println("cntOfMale");
        System.out.println(cntOfMale);
//        输出
//        avgAge of class : 信管191
//        22.0
//        cntOfFemale
//        0
//        cntOfMale
//        6
    }
 
    public static void main(String[] args) {
        calSchool();
//        第四题
//        avgClassStuCnt
//        6.0
    }
}