吴裕雄--天生自然java开发常用类库学习笔记：多对多关系范例

import java.util.List ;
import java.util.ArrayList ;
public class Course{
    private String name ;
    private int credit ;
    private List<Student> allStudents ;
    public Course(){
        this.allStudents = new ArrayList<Student>() ;
    }
    public Course(String name,int credit){
        this() ;
        this.name = name ;
        this.credit = credit ;
    }
    public List<Student> getAllStudents(){
        return this.allStudents ;
    }
    public void setName(String name){
        this.name = name  ;
    }
    public void setCredit(int credit){
        this.credit = credit ;
    }
    public String getName(){
        return this.name ;
    }
    public int getCredit(){
        return this.credit ;
    }
    public String toString(){
        return "课程名称：" + this.name + "；课程学分：" + this.credit ;
    }
};

import java.util.List ;
import java.util.ArrayList ;
public class Student{
    private String name ;
    private int age ;
    private List<Course> allCourses ;
    public Student(){
        this.allCourses = new ArrayList<Course>() ;
    }
    public Student(String name,int age){
        this() ;
        this.name = name ;
        this.age = age ;
    }
    public List<Course> getAllCourses(){
        return this.allCourses ;
    }
    public void setName(String name){
        this.name = name ;
    }
    public void setAge(int age){
        this.age = age ;
    }
    public String getName(){
        return this.name ;
    }
    public int getAge(){
        return this.age ;
    }
    public String toString(){
        return "学生姓名：" + this.name + "；年龄：" + this.age ;
    }
};

import java.util.Iterator ;
public class TestMore{
    public static void main(String args[]){
        Course c1 = new Course("英语",3    ) ;    // 第一门课程
        Course c2 = new Course("计算机",5) ;    // 第二门课程
        Student s1 = new Student("张三",20) ;
        Student s2 = new Student("李四",21) ;
        Student s3 = new Student("王五",22) ;
        Student s4 = new Student("赵六",23) ;
        Student s5 = new Student("孙七",24) ;
        Student s6 = new Student("钱八",24) ;
        // 第一门课程有三个学生参加
        c1.getAllStudents().add(s1) ;
        c1.getAllStudents().add(s2) ;
        c1.getAllStudents().add(s6) ;
        s1.getAllCourses().add(c1) ;
        s2.getAllCourses().add(c1) ;
        s6.getAllCourses().add(c1) ;
        // 第二门课程有六个学生参加
        c2.getAllStudents().add(s1) ;
        c2.getAllStudents().add(s2) ;
        c2.getAllStudents().add(s3) ;
        c2.getAllStudents().add(s4) ;
        c2.getAllStudents().add(s5) ;
        c2.getAllStudents().add(s6) ;
        s1.getAllCourses().add(c2) ;
        s2.getAllCourses().add(c2) ;
        s3.getAllCourses().add(c2) ;
        s4.getAllCourses().add(c2) ;
        s5.getAllCourses().add(c2) ;
        s6.getAllCourses().add(c2) ;
        // 输出一门课程的信息，观察一门课程有多少个学生参加
        System.out.println(c1) ;
        Iterator<Student> iter1 = c1.getAllStudents().iterator() ;
        while(iter1.hasNext()){
            Student s = iter1.next() ;
            System.out.println("	|- " + s) ;
        }
        // 通过学生找到学生参加的课程
        System.out.println(s6) ;
        Iterator<Course> iter2 = s6.getAllCourses().iterator() ;
        while(iter2.hasNext()){
            Course c = iter2.next() ;
            System.out.println("	|- " + c) ;
        }
    }
};