数据表与简单Java类（多对多的关系）

 

public class Newbegin{
public static void main(String args[]) {
 //第一步：根据结构进行关系设置
 //1.创建各自的独立对象
 Student stu1=new Student(1,"张三",18);
 Student stu2=new Student(2,"李四",19);
 Student stu3=new Student(3,"王五",18);
 Course ca=new Course(1001,"马克思主义哲学",3); 
 Course cb=new Course(1002,"操作系统",2);
 //2.设置学生和课程的关系，这里面需要准备出成绩
 stu1.setStudentCourse(new StudentCourse[]{
  new StudentCourse(stu1,ca,99.9),
  new StudentCourse(stu1,cb,87.0),
 });
 stu2.setStudentCourse(new StudentCourse[]{
  new StudentCourse(stu2,ca,78.9),
 });
 stu3.setStudentCourse(new StudentCourse[]{
  new StudentCourse(stu3,cb,98.0),
 });
 //3.设置课程和学生的关系
 ca.setStudentCourse(new StudentCourse[]{
  new StudentCourse(stu1,ca,99.9),
  new StudentCourse(stu2,ca,78.9)
 });
 cb.setStudentCourse(new StudentCourse[]{
  new StudentCourse(stu1,cb,87.0),
  new StudentCourse(stu3,cb,98.9)
 });
 //第二部：根据结构取出数据
 //1.可以找到一门课程，以及参加此课程的所以学生信息，和他的成绩；
 System.out.println(ca.getInfo());
 for(int x=0;x<ca.getStudentCourse().length;x++){
  System.out.print("	|-"+ca.getStudentCourse()[x].getStudent().getInfo()); 
  System.out.print(",成绩："+ca.getStudentCourse()[x].getScore());
  System.out.println();
 }
 //2.可以找到一名学生，以及参加的课程信息，和他的成绩
 System.out.println("========================");
 System.out.println(stu1.getInfo());
 for(int x=0;x<stu1.getStudentCourse().length;x++){
  System.out.print("	|-"+stu1.getStudentCourse()[x].getCourse().getInfo());
  System.out.print(",成绩："+stu1.getStudentCourse()[x].getScore());
  System.out.println();
 }
}
}
class Student
{
 private int stuid; 
 private String name;
 private int age;
 private StudentCourse studentCourse[];
 public Student(){}
 public Student(int stuid,String name,int age){
  this.stuid=stuid;
  this.name=name;
  this.age=age;
 }
 public void setStudentCourse(StudentCourse studentCourse[]){
  this.studentCourse=studentCourse;
 }
 public StudentCourse[] getStudentCourse(){
  return this.studentCourse;
 }
 public String getInfo(){
  return "【STUDENT】学生编号："+this.stuid+",姓名："+this.name+",年龄："+this.age;
 }
}
class Course
{
 private int cid;
 private String name;
 private int credit;
 private StudentCourse studentCourse[];
 public Course(){} 
 public Course(int cid,String name,int credit){
  this.cid=cid;
  this.name=name;
  this.credit=credit;
 }
 public void setStudentCourse(StudentCourse studentCourse[]){
  this.studentCourse=studentCourse;
 }
 public StudentCourse[] getStudentCourse(){
  return this.studentCourse;
 }
 public String getInfo(){
  return "【COURSE】课程编号："+this.cid+",名称："+this.name+",学分："+this.credit;
 }
}
class StudentCourse//学生选课
{
 private Student student;
 private Course course;
 private double score; 
 public StudentCourse(){}
 public StudentCourse(Student student,Course course,double score){
  this.student=student;
  this.course=course;
  this.score=score;
 }
 public Student getStudent(){
  return this.student;
 }
 public Course getCourse(){
  return this.course;
 }
 public double getScore(){
  return this.score;
 }
}