tesGet出错？
package com.imooc_collection;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/*
* 备选课程类
*/
public class ListTest {
/**
* 用于存放备选课程的List
*/
public List coursesToSelect;
public ListTest(){
this.coursesToSelect=new ArrayList();
}
/**
* 用于王coursesToSelesect中添加备选课程
*/
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);
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);
Course cr3 = new Course("3","JAVA入门到转行");
coursesToSelect.add(0,cr3);
Course temp3 = (Course) coursesToSelect.get(0);
System.out.println("添加了课程"+temp3.id+":"+temp3.name+"");
/*
* 以下会抛出数组下标异常
* Course cr3 = new Course("3","JAVA入门到转行");
* coursesToSelect.add(4,cr3);
*/
Course[] course = {new Course("4","离散数学"),new Course("5","汇编语言")};
coursesToSelect.addAll(Arrays.asList(course));
Course temp4 = (Course)coursesToSelect.get(3);
Course temp5 = (Course)coursesToSelect.get(4);
System.out.println("添加了两门课程"+temp4.id+":"+temp4.name+"和"+temp5.id+":"+temp5.name+"");
Course[] course2 = {new Course("6","高等数学"),new Course("7","大学英语")};
coursesToSelect.addAll(2, Arrays.asList(course2));
Course temp6 = (Course)coursesToSelect.get(2);
Course temp7 = (Course)coursesToSelect.get(3);
System.out.println("添加了两门课程"+temp6.id+":"+temp6.name+"和"+temp7.id+":"+temp7.name+"");
/*
* 取得List中元素的方法
*/
public void testGet(){
int size = coursesToSelect.size();
System.out.println("有如下课程待选：");
for(int i=0;i<size;i++){
Course cr = (Course)coursesToSelect.get(i);
System.out.println("课程："+cr.id+":"+cr.name);
}
}
}
public static void main(String[] args){
ListTest lt = new ListTest();
lt.testAdd();
lt.testGet();
}
}
如图，代码会出现这种错误，这里暂时只贴出主函数，其他类确保和老师的一样了。我该怎么解决？
