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〖第13章：Java类集〗_范例讲解：多对多关系

发布时间：2021-01-04 16:46:26编辑：雪饮阅读（）

 学生与所学技能之间，一个学生可以学习多个技能，一个技能可以被多个学生学习，这样就形成了多对多的类集范例。

import java.util.List ;
import java.util.ArrayList ;
import java.util.Iterator ;
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;
       }
};
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 + ",学生年龄:" + this.age ;
       }
};
public class Hello{
   public static void main(String args[]){
              Course c1 = new Course("天舞烈风",3      ) ;
              Course c2 = new Course("烈风连脚",5) ;
              Student s1 = new Student("kasumi",20) ;
              Student s2 = new Student("ayane",21) ;
              Student s3 = new Student("momiji",22) ;
              Student s4 = new Student("hayabusa",18) ;
              Student s5 = new Student("lisa",24) ;
              Student s6 = new Student("snowDrink",24) ;
              //天舞烈风有3个学生学习
              c1.getAllStudents().add(s1) ;
              c1.getAllStudents().add(s2) ;
              c1.getAllStudents().add(s6) ;
              s1.getAllCourses().add(c1) ;
              s2.getAllCourses().add(c1) ;
              s6.getAllCourses().add(c1) ;
              //烈风连脚有6个学生学习
              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) ;
              //查看天舞烈风技能有哪些学生在学习
              Iterator<Student> iter1 = c1.getAllStudents().iterator() ;
              while(iter1.hasNext()){
                     Student s = iter1.next() ;
                     System.out.println("\t|- " + s) ;
              }
              //查看snowDrink学生学习了哪些技能
              System.out.println(s6) ;
              Iterator<Course> iter2 = s6.getAllCourses().iterator() ;
              while(iter2.hasNext()){
                     Course c = iter2.next() ;
                     System.out.println("\t|- " + c) ;
              }
   }
};