为什么我的代码在第二个数组的时候，输出时的下标是2，3.而不是接着下去的5，6呢
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();
}
/*用于往coursesToSelect中添加备选课程List 中
*
* */
public void testAdd() {
/*创建一个课程对象，并通过调用add 方法，添加*/
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","test");
coursesToSelect.add(0,cr3);
Course temp3=(Course)coursesToSelect.get(0);
System.out.println("添加了课程："+temp3.id+":"+temp3.name);
Course[] course= {new Course("3","离散数学"),new Course("4","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+";"+temp5.id +":"+temp5.name);
Course[] course2= {new Course("5","高等数学"),new Course("6","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+";"+temp7.id +":"+temp7.name);
}
public static void main(String[] args) {
ListTest It =new ListTest();
It.testAdd();
}
}
