public static void main(String[] args) {

SetTest st = new SetTest();// TODO Auto-generated method stub

st.testAdd();

st.testForeach();

Student student = new Student("131820","李宇曜");

System.out.println("欢迎学生"+student.id+' '+student.name+"选课");

Scanner console = new Scanner(System.in);

for(int i=0;i<3;i++){

System.out.println("请选择第"+i+"课程");

String courseId = console.next();

for(Course cr:   st.coursesToSelect){        为什么写coursesToSelect会报错

if(cr.id.equals(courseId)){

student.courses.add(cr);

}