为什么我无法加入到已选课程中，courses中没有添加到课程
package com.imooc.collection;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
public class SetTest {
public List<Course> courseToSelect;
public SetTest(){
courseToSelect=new ArrayList<Course>();
}
public void testAdd(){
// 创建一个课程对象，并通过调用add方法，添加调用add方法，添加到备选课程;List中
Course cr1=new Course("1.","数据结构");
courseToSelect.add(cr1);
Course temp=(Course) courseToSelect.get(0);
// System.out.println(temp.id+temp.name);
Course cr2=new Course("2.","C语言");
courseToSelect.add(1,cr2);
Course temp2=(Course) courseToSelect.get(1);
// System.out.println(temp2.id+temp2.name);
Course[] cr3={new Course("3.","离散数学"),new Course("4.","汇编语言")};
courseToSelect.addAll(Arrays.asList(cr3));
Course temp3=(Course) courseToSelect.get(2);
Course temp4=(Course) courseToSelect.get(3);
// System.out.println(temp3.id+temp3.name+temp4.id+temp4.name);
Course[] cr4={new Course("5.","算法"),new Course("6.","大学英语")};
courseToSelect.addAll(0,Arrays.asList(cr4));
Course temp5=(Course) courseToSelect.get(4);
Course temp6=(Course) courseToSelect.get(5);
// System.out.println(temp5.id+temp5.name+temp6.id+temp6.name);
}
public void foreach(){
System.out.println("foreach");
for(Course cr:courseToSelect){
System.out.println(cr.id+cr.name);
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
SetTest st=new SetTest();
st.testAdd();
st.foreach();
Student student=new Student("1","小米");
System.out.println("欢迎"+student.name+"选课");
Scanner console=new Scanner(System.in);
for(int i=0;i<3;i++){
System.out.println("输入课程ID");
String courseId=console.next();
for(Course cr:st.courseToSelect){
if(cr.id.equals(courseId)){
student.courses.add(cr);
}
}
}
st.tesx(student);
System.out.println(student.courses.size());
}
public void tesx(Student student){
for(Course cr:student.courses){
System.out.println(cr.id+cr.name);
}
}
}
//学生类
package com.imooc.collection;
import java.util.HashSet;
import java.util.Set;
public class Student {
public String id;
public String name;
public Set<Course> courses;
public Student(String id, String name) {
this.id = id;
this.name = name;
this.courses = new HashSet<Course>();
}
}
//Course 类
package com.imooc.collection;
public class Course {
public String id;
public String name;
public Course(String id, String name) {
this.id = id ;
this.name = name;
}
public Course() {
}
}
