为什么是temp的id和name，不是cr1的id的id和name？

package com.imooc.cellection;

import java.util.Arrays;

import java.util.List;

import java.util.ArrayList;

public class ListTest {

   public List coursesToSelect;

   public ListTest(){

  this.coursesToSelect = new ArrayList();

   }

   public void testAdd(){

  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);