为什么还要定义一个对象temp呢？
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);
}
