JAVA进阶ArrayList的节点删减

import java.util.*;
public class Test{
public static void main(String[] args){
ArrayList aa1=new ArrayList();
System.out.println("大小为"+aa1.size());
Xs xs1=new Xs("悟空",15,90);
Xs xs2=new Xs("八戒",13,70);
Xs xs3=new Xs("沙僧",14,75);
Xs xs4=new Xs("小白龙",20,80);
aa1.add(xs1);
aa1.add(xs2);
aa1.add(xs3);
System.out.println("大小为"+aa1.size());
for(int i=0;i<aa1.size();i++){
Xs tv=(Xs)aa1.get(i);
System.out.println("第"+(i+1)+"个学生姓名是"+tv.getXingming());

}
aa1.remove(1);//把1的位置数据删掉，之后的数据依次跟上补位。
aa1.add(1,xs4);//1就是在1的位置插入数据，如果没有1，则默认在尾部添加。
for(int i=0;i<aa1.size();i++){
Xs tv=(Xs)aa1.get(i);
System.out.println("第"+(i+1)+"个学生姓名是"+tv.getXingming());
}
}
}
class Xs{
private String xingming;
private int xuehao;
private int chengji;

Xs(String xingming,int xuehao,int chengji){
this.xingming=xingming;
this.xuehao=xuehao;
this.chengji=chengji;
}
public String getXingming(){
return xingming;
}
public int getXuehao(){
return xuehao;
}
public int getChengji(){
return chengji;
}
}