public void Listadd(){
    Course cr1=new Course("1","数据结构");
    coursesToSelect.add(cr1);
    Course temp =(Course)coursesToSelect.get(0);
    System.out.println("添加了课程："+temp.id+temp.name);

    Course cr2=new Course("2","C语言");
    coursesToSelect.add(0,cr2);
    Course temp2 =(Course)coursesToSelect.get(0);
    System.out.println("添加了课程："+temp2.id+temp2.name);
}