范例讲解：一对多关系
public class Student{private String name ;private int age ;private School school; // 一个学生属于一个学校public Student(String name,int age){this.setName(name) ;this.setAge(age) ;}public void setSchool(School school){this.school = school ;}public School getSchool(){return this.school ;}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 ;}}

?学校类

import java.util.List ;import java.util.ArrayList ;public class School{private String name ;private List<Student> allStudents ;public School(){this.allStudents = new ArrayList<Student>() ;}public School(String name){this() ;this.setName(name) ;}public void setName(String name){this.name = name ;}public String getName(){return this.name; }public List<Student> getAllStudents(){return this.allStudents ;}public String toString(){return "学校名称：" + this.name ;}}

?关系测试类

import java.util.Iterator ;public class TestDemo{public static void main(String args[]){School sch = new School("清华大学") ;// 定义学校Student s1 = new Student("张三",21) ;Student s2 = new Student("李四",22) ;Student s3 = new Student("王五",23) ;sch.getAllStudents().add(s1) ;sch.getAllStudents().add(s2) ;sch.getAllStudents().add(s3) ;s1.setSchool(sch) ;s2.setSchool(sch) ;s3.setSchool(sch) ;System.out.println(sch) ;Iterator<Student> iter = sch.getAllStudents().iterator() ;while(iter.hasNext()){System.out.println("\t|- " + iter.next()) ;}}}

?输出结果：

学校名称：清华大学|- 学生姓名：张三；年龄：21|- 学生姓名：李四；年龄：22|- 学生姓名：王五；年龄：23

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